[Involved] Crazy MPFI, mind of its own

[fmc351]

Yeah I know, Im a noob and hitting you with a problem, but hopefully someone here will know whats going on, before I beat the aging baldness and deliver my own. The things driving me nuts.

Starting problem
1988 EA wagon (S, MPFI, 5 spd manual), starts usually on the third turn of the key (I dont hold it cranking endlessly until it starts, i just wind it for a few seconds (maybe 5), then try again). By the third attempt it starts. Idles at about 800 rpm, then settles down to maybe 650 - 700. I have tried just letting the pump prime the lines, ie: key on until pump shuts off, then off/on again, repeat 3 times, but it makes no difference. Still takes three lots of actual cranking to fire up.

Once running, still cold
Once running, from cold, and slight downhill from home to the corner, I can 1/4 the pedal and it takes off and revs out to 4,000 no worries (I dont usually reline it, so it would likely rev harder). Once it warms up, it wont rev past 2,000. I need to ride the clutch to take off. Once its moving and if I slowly feed it pedal, it will rev past 2,000 but very slowly (like driving a diesel).

Highway cruising
While cruising on the highway (flat road at around 1900 rpm to do 100 kmh), it will cough, seems to cut out, fire up, cut out etc. Occasionally I can smell its leaning out, other times it uses excessive fuel. When it cuts out, if I take my foot off the pedal, and replace it down slightly it will take off, then cut out again, until it decides to run fine. It often runs absolutely fine too, but I can never give it a bootful and take off, it will just splutter.

Idle
It often idles fine, but occassionally it will hunt, or close to stall, then back to either 650-700 rpm or resumes hunting. But I can leave it at idle for 5 minutes and it just sits there idling fine, other times it will start hunting within 30 seconds or so of letting it idle.

Under Load
Theres a particular hill near home, if I take it at 110 kph, it may fly up at 110, other times it will drop back to 80 and I drop back to 3rd to hold it there, and it usually holds at 70-80 kmh.

Anyway, theres probably more symptoms but thats all I can think of now. Ive replaced a few parts, and used a few test parts, but cant correct it, it remains exactly the same.

Brand new parts replaced.
Dissy is a complete replacement from Bosch. Incl TFI, and hall effect, rotor button and cap
New champion leads and ngk plugs.
New bosch alternator (85 amp)
New VDO fuel pump.
Inlet manifold gasket.


Swapped injectors and rail for known working ones.
Have replaced EFI and fuel pump relays with known working ones. (Twice)
Same with fuel regulator.
Same with MAP sensor
Used a mates ECU (EA 3spd auto MPFI, mines a 5 spd manual MPFI). Numbers on ECU are the same, except for one letter. His is a 7a, mines a 7b, or vice versa)

Left to play with are.
O2 sensor
Coolant temp sensor
ISC solenoid
TPS
Throttle body. <<<<Likely, feels like a dead spot maybe, but doesnt explain the intermittant hunting, and occassional running fine, could be wrong though
Wiring

I looked for an airflow meter, but cant seem to locate it.

Any ideas. Or should I just burn it? Tell you what, ive come close.
Thanx in advance.

[EFFalcon]

there isnt an airflow sensor, the MAP sensor does the job.
i assume the dizzy used was a MPFI one? same with the fuel pump?

[fmc351]

Originally Posted by EFFalcon

there isnt an airflow sensor, the MAP sensor does the job.
i assume the dizzy used was a MPFI one? same with the fuel pump?

Yeah both MPFI versions.

I didnt think I saw an air flow meter. Cool, one down.

[Brent79]

is your timing Ok?

Brent

what conditon is your map sensor hose in? if these are cracked and there is a drop in vacume it will give wrong signals to the sensor.

[fmc351]

Timing is OK. When I did the dissy, I set the base timing. It didnt hunt at all, so I believe its fine. Theres no pre-ignition, so I assume its all OK. I dont think it would explain being unable to rev out at all though IMO. By rev out, I mean to even 3,000 when warm


MAP sensor hose looks fine, what I can see of it. Its not brittle at all, but might have to check that out more, thanx. Theres just no room to fit my clams in there to check it all properly, Im not looking forward to that.

[Brent79]

Hmmm... your problem sounds similar to mine.... cept my car starts first kick. Has its days on wheather it wants to rev out or not... hunts like CRAZY espesh when the A/C is on... You got any ECU fault codes?

Brent

[fmc351]

Oh I got fault codes. Ignition on, not running code, 11, No faults. Shes a ripper.

Running I get code 41 (?If a recall it?), which indicated ISC, manifold leaks and a heap of others. Replaced the inlet gasket, as code 41 said it could be one, and on here I read they can suck them in. It was fine but hard and brittle, changed that earlier tonight.

I just dont want to replace any more parts until I have a good indication of which it is. The car aint worth that much $$$$. Its just a stock EA wagon, its clean and straight, but still.

I would think a leak could be the throttle body butterfly or any of the million and one hoses.
The pedal response to the problems described make me think TPS or throttle body.
The lean out, and excessive fuel make me think O2.
Crazy idle makes me think ISC. Although any of the others could cause idle dramas.

Sorry, im just bouncing thoughts.

[Brent79]

ahhh, code 41 indicates low O2 voltage (lean) - I too get this... Hmmmmm

Brent

[Brent79]

*looks up book* Code 41 - O2 Voltage less than 0.5V - Symptoms include running rough, hesitation and stalls, runs lean. If O2 sensor faulty, will correct to rich thus indicating fouled spark plugs. Other causes for code are Engine misfire, exhust manifold leak or low MAP sensor voltage, fuel starvation.

Brent

[fmc351]

Yeah, it could be 42, as I said I not sure. Its 40 something, the one with heaps of possible faults in the Gregorys manual. Great help I found it, well at least I knew it wasnt tail lights. :

I remember it also listed ISC as one possible fault and manifold leaks, I think even coolant temp sensor.

O2 sensor is likely. I cant imagine they stand the heat to well, so would likely die easily.

Hopefully someone will be able to say, yeah mate its the ????. Happens all the time. I really want to avoid the process of elimination cure.


By Friday I could be buying marshmallows.

[Brent79]

From my experience tho, ive found that faulty sensors dont really effect your car to the extent as most people think. The ECU will use a default map for any sensor that goes "out of range" so really it shouldnt cut out or stall out like you mentioned. Its probably something thats triggering the faults. On my EA wagon, its was a collapsed brake vacuum hose which was leaking vacuum right next to the MAP feed hose which caused hesitation under load and bad starting... ECU spat out all sorts of codes.. fixed the hose and ran a code 11

Brent

[fmc351]

OK. Im pretty sure the brake vacc line is good. But then I never see it under real manifold pressure. In neutral and reving, the vaccum is not the same as driving.

it actually plays up in neutral too though, much the same. Wont rev past maybe 2-2500 rpm. It will go higher but only if you feed it slowly. Sometimes it will hold at the revs, other times it will breakdown. Other times it wont rev up at all, without spluttering. Maybe if the sensor is intermitantly faulty, or kinda OK, it will cause the issues. Ive got no idea. I prefer carb and electronic ignition. Lifes so simple then.

I thought if the sensor is faulty, it will cause issues. Ill have a better look tomorrow at the O2 sensor and test it for voltage, at the plug, and the sensor. It seems most likely. It could be a combination of sensors too. Unlikely I would have thought, but one faulty part could strain another.

Whats the resistance supposed to be on a good O2 sensor?

[fmc351]

Update: Replaced the O2 sensor with a known good one. Nothing different.

I did notice a sensor (at least an electrical connection) on the underside of the inlet manifold next to the MAP sensor air vacuum feed at the manifold. What the hell is that?

Brake vacuum line seems fine, so does MAP sensor vacuum line.


I did notice when I reset the computer, and started it, it took forever for the computer to set itself. For a minute or so, idle smooth. But then starts to hunt around, nearly stalling, rev up, keeps doing that then stalls. Start it sraight away, same again. After about 20 minutes and about 30 restarts, it seems to be idling OK, but still hunts occasionally. If i give it pedal to 2,000 rpm, and hold it, it drops to 1800, back to 2000 and wanders around those revs.

[Brent79]

Hmmmm.... what kinda cam u got in it? standard one?? That connector, whats it look like? round? how many contacts, one or two?

Brent

[fmc351]

Note there are 2 switches Im referring to in this post.
One is the one mentioned earlier, actually threaded into the inlet manifold, on the engine block side. It looks similar to a temp guage switch off an old x-flow. Thats what i thought it might be, an air temp sensor. I think it has just 2 push on connections, Im not certain, and the cars not here now to check. Ill will look later.

The other switch is some ??gas?? system wiring stuff on the firewall next to the map sensor. Its never been on gas as long as Ive had it, and no extra filler holes, or anything to plug them up, so im not certain it had gas. Maybe it was alarm immobiliser or something. Yesterday i located some wiring that wasnt meant to be there. It was only a part of some aftermarket curcuit, the rest had been removed previously by whoever. The only bit left was a fuel cut out switch (so the sticker on the back of it says), when i saw it, i though yeah, thats it. It had been fitted into the efi loom which it was still connected to, and the other end went into the cabin under the dash, to nothing, just hanging there taped up. I thought I was on a winner here.

The section of the aftermarket loom that was still connected was all in teh engine bay. One wire was used to bypass the ISC orange wire, bypassed by cutting the original orange wire which was cut at the ISC connector plug, upto said ?gas? switch, and a wire fed from the switch back into the other end of the looms orange wire in the round loom plug at the firewall end of the rail. There were a couple of other wires piggy backed into this curcuit from various connectors on the switch. I assume it was a gas setup, ??the switch for petrol/gas?? Anyway its all removed now, the old wiring that was bypassed has been resoldered together and heatshrinked, and its running, but no better. The aftermarket curcuit could have done something, but it hasnt changed the problems by removing it. I just feel better having done it. Unless its fried something.

Cam? I didnt fit it what ever it is. Sounds standard, never flogged it before so dont know. ill assume not. Nah its not worked, if anything probably a gas cam. But it did run perfect when i first got it. Revved no drama.

Ive got hold of an ISC, gonna plug and play that.

[TUFED6]

Have to say, sounds like a fuel supply problem. You sure the new pump was an MPFI one?

Have you changed the fuel filter? Also might be worth blowing the fuel lines out with a compressor.

Maybe get a fuel pressure gauge and rig it up so you can monitor the pressure in the injector rail while you are driving.

I had a wierd problem like this with my ED years ago, turned out a small piece of gravel had found its way into the fuel line, and was sitting at the entry of the fuel filter. The surging you describe sounds familiar.

- John

P.S. Love your avatar. You know why I pulled you over? Littering...

[IH8HSV]

How about looking at a different approach.
My brothers EA had similar problems - good idle , bad idle , high revs , low revs , cut outs... e.t.c.... the list went on. It turned out to be a slight crack in the head gasket. Im hoping its not - but just another suggestion. We too replaced dizzys , pumps , hoses e.t.c. and after that trouble we ended up spending more on parts than getting the head replaced!!!

Good luck

[oyob2003]

Hi, have a look at the "AutoTap" site when there click on how to articals.........ken

[MAD]

When the car is cold the engine runs in without taking any info from the sensors in regard to the running of the engine, but once its warm, the ECU takes proper control of the engines fuel supply and spark system.
So to me this points to 'something' that is used when the engine is warmed, yes a very wide net but at least its something. It rules out base timing issues and most likely rules out a head gasket or fuel supply too.

It sounds, to me, a little like its going in to limp home mode although I'm not really clued up on the OHC engine, and what would cause this to happen.

When you took the KOEO codes did you wait for the memory codes?

[BENT_8]

I had my car to a ford dealer back in early january with similar problems to yours. I travelled 120kms and used 1/2 of a tank on the highway and when i arrived it ran like a dog, hunted and had a strong fuel smell.
whenever i give it a feed it feels as though it is being held back over 3500rpm.
The ford dealer ran the diagnostic and it came back as coolant temp sensor.
The boys at ford said it was telling the ECU that the car wasnt warming up and therefore maintaining a rich mixture like a choke would do.
Just a thought as it was on your things still to check list.
good luck

[fmc351]

Ken, where for is this Autop tap site. I checked the links at the top, cant see it. Forgive me, Im a noob.

I replaced fuel filter when I did the pump, Im sure its MPFI pump, I trust the guy at the local auto shop, hes good on that type of info, been around a while. But if all else fails I will fit a pressure guage to the line if I can lay my hands on one.

Its not losing water, the oils fine, so head gasket is unlikely I hope. But hey, it still does get warmish (sits between O and R of the NORMAL range currently). But im leaning towards it being a fuel/air ratio thing.

I did wait for all codes. I got 11. Both sets of KOEO (I like the abbrev, cheers) codes, and obviously the repeats.

I remembered I stripped an EA Fairmont Ghia and kept a heap of EFI parts. So i went to the container today and raided. Fitted a working coolant temp sensor, then an ISC. Original ISC was cleaner, the spare ones housing was full of corrosion (green powder). I pulled the spare solenoid from the housing, and fitted it to my housing, new gasket on ISC to throttle body. Start car, idled fine, 800 rpm, smooth and constant. Boot peddle to floor, light deadspot, air roar, and rev. SWEET JESUS. Went for a run, peddle hard, 4,500, 2nd same, third 3000 pull up at crossroad. Take off wont rev past 2500. But no problem with idle and will take off without serious problems, it just hesitates for a second, then goes upto 2500. Cool, it runs without causing whiplash

Go back, test codes, KOEO, all 11's.

Running codes, first time, it ID'd the ECU as an AUTO 3.9 MPFI. wtf? Its a manual.
(13) ISC (So the mix of original and spare are better but not right). Will get a good one tomorrow.
(63), TPS



So im confused on the ECU ident. Its a manual 3.9 MPFI. So I run test it again, maybe I miscounted flashes.
Now it wont ID the ECU, it just jumps into the codes. However this time different codes.
(12) ISC, ok thats confirmed
(41), the catch all. Ive also got a spare Air temp sensor which is part of code 41 (yeah thats the switch under the manifold, facing the block, I worked that out).

I retested about 5 times, twice it Id'd the ECU as auto. The rest of the times, it failed to id the ECU at all, just went to the codes (if Im readin them right).

I drove it about 15 km's, country road. It ran at 2,000rpm, 110km, up hills with very few dramas. Occasionall Id need to take foot off pedal and ease it back on up hills. To do 100, I usually need only just touch the pedal, its that way now too. So having to back off pedal and replace foot seems like TPS is faulty, one set of codes ID'd it as so too. Ill get one of them too.

So the ECU ident still has me baffled, it may be an auto one. Any info appreciated here. i took down the numbers of the ECU. Anyone know what they are. Ill ring Ford tommorrow if i cant find it here somewhere with a search.

Numbers on ECU
88HO5
EECIV EFI - SD153
*783* 87DA-12A650-AC
8HO54 7DAC

Maybe the ECU is the drama all along, and a few dicey sensors. Its been a headf*&^
Seriously, thanks to everyone, my posts have been long winded and I appreciate everyone taking the time to read it. Brent, someone to bounce ideas off has helped me to work out what im actually thinking. Cheers.


madxf, im prefer an x series myself. Im sitting on a XC GXL 78 update, I need to get some good doors and guards. The shells good, no pillar rot, boot rot or inner guard rot, inside stays dry. Got a strong 351C built by an old school drag racer on the Sunny Coast Qld (George Wegener), just waiting to go in to its new home. 9" LSD disc, still need to source a good box. Im leaning towards an AOD, with 2,800-2,900 stall (should suit the cam well). Need to rebuild the 9" too, maybe 3.25-55. Maybe Ill get to that one this year.

[Brent79]

Thats def a manual ECU code, 3.9 MPI Manual
Make sure when u change something u reset the memory codes (by disconnecting self test input during code read) so u dont get em repeating old codes... TPS sounds bout right... would effect idle and cause hesitations... code 13 shouldnt appear on a MPI ecu, its to do with the CFI idle motor. Strange....

Brent

[Brent79]

ooops sorry, code 13 can be on MPI ecu... means isc is getting stuck... throttle by-pass open

Brent

[fmc351]

Originally Posted by Brent79

ooops sorry, code 13 can be on MPI ecu... means isc is getting stuck... throttle by-pass open

Brent

Sticking? In the housing or the solenoid? Either? Can I just clean out the housing?


Ok, found a thread referring to the exact question on auto/manual ECU. The "A" in 7DAC means its a manual. *relaxes pooper* So why the auto code? Must have read it wrong, or the ECU has gremlins

[Brent79]

Read it again, if it definately reads as an auto, id be changing the ECU. With regards to the code 13, Ford EFI management book says it means car doesnt return to idle, id expect this to mean the ISC plunger is sticking or not closing properly. Try spraying somesorta lube in it. Remove the solenoid and plunge it by hand to see if it opens and closes ok...

Brent