Black88Z

Ok, well i thought the problem was gone, but its back!

First off, i'd like to say sorry for the very long post lol. I have an 88 iroc z with a 350TPI, and im almost positive my problem is fuel related.

It runs fine when cold, but when its warmed up it will sputter, miss, and have absolutly no power. I usually cant get it over 1500rpms. If i romp on it it does absolutely nothing, and if i keep it down for more than a few seconds it will stall. It will always stall eventually. If i get out, adjust the TPS from the .54 to about .60 -.75, it will stay running, and drive ok, but still not right (obviously). Im at least able to limp it home this way (knock on wood). Its got me kinda confused, i thought it was just the TPS out of adjustment but i guess not. It ran ok after re-adjusting the TPS the first time, but now its pretty much back to how it was.

My fuel pump squeels pretty much at all times, when i first got it it only did on start up, but now its always squeeling. The guy said he put a new fuel pump and filter in, and cleaned the tank out, but who knows if he really did or not. He said its an aftermarket pump and alot of them squeel. I dont have a way of testing the fuel pressure, so that hasnt been done yet.

I ohmed 2 of my injectors out and they were ok, but the clip that holds the connector on broke on both of them, so i didnt want to risk breaking all the clips trying to test the injectors. I havent had any problem with them unplugging (to my knowledge), so i suppose maybe i should just take the chance and ohm them.

I seafoamed the HECK out of the car, seafoam thru the tank, oil, brake booster line, TB. It smoked like CRAZY! My fathers dark blue 17ft long suburban was parked behind it a few feet, you literally could not see the truck thru all the smoke coming from the exhaust. I have seafoamed alot of cars and always had a great reaction from it, but this was twice as much smoke as my previous best smoke-out. It helped alot (obviously lol), afterwards it idled alot better and the throttle response was noticable better too.

I thought MAYBE because it smoked so much it fouled up the O2 sensor real bad causing it to run the way it is. I thought it was a long shot, but from working on cars ive learned anything can happen. Im going to try unplugging the O2 sensor and driving it around like that for a little bit, to see if it still will give me the same problems.

I have checked the TPS, it is adjusted correctly and works fine.

Its got a new cap, rotor, and plug wires. I have not replaced the plugs yet, but that wouldnt cause the problem im having anyways.

I have not had the ign. module tested yet.



I appreciate all help with this, i really am at a standstill here with it. This is my daily driver car, so i really need to get it running right ASAP. Thanks for taking the time to read the entire post lol, i know its pretty long. -Adam

ahankins32984

Hey I have a 86 Z28 305 TPI and I had the same exact issue with mine the issue with my car wound up being Fuel pump clogged up and alot of sludge in the tank I had my tank and pump replaced and now she is running like a champ so I would definitely check the fuel pressure ASAP it should be at 30 to 45psi

Black88Z

Hey man, thanks for the response. I'd like to check it,but i have no way of checking it. Do you know of any places that rent/loan out fuel pressure test gauges? Ie pep boys, auto zone, ect.?

Anything else it could be? Any other ideas? Its really got me confused lol.

torque_is_good

yes, it could be that the fuel pump is getting hot. Do you have greater than 1/4 tank of gas?

does it really run well when cold?

if so, disconnect the wire to the MAF and the car will throw a check engine light (forcing the car into open loop)but see if the problem goes away. If it does, then it's a sensor and probably an O2 sensor

Black88Z

Well neither the tach nor the fuel guage work, so i always fill it up and make sure to stay on top of it so i dont run out. I filled it a few days ago and havent driven it much because of how its running, so id say its probably 3-4th tank to 1/2 at the very lowest. Im positive its over 1/4, and ive always had the problem, even right after i fill it.

I went out and tried unplugging the O2 sensor and the MAF and drove it, it ran way worse with the O2 unplugged, a little better than that with the MAF unplugged, but was definetly better with them both plugged in.

Im not really sure its a sensor, it could be the CTS, maybe the MAT, but i kinda think it may be the fuel pump or a bad injector. If it was the CTS or MAT, it would run crappy at any rpm, even idle, right? Maybe not, but thats what i was thinking.

When it was warm and i plugged everything back in i romped on it real quick, to get it to miss and start sputtering, and held it at about 3/4th throttle. It was sputtering, missing, and backfiring thru the exhaust, i could hear it thru the exhaust and feel it thru the gas pedal. It kinda felt like it was running on 4-6 cylinders i would say, and like it had a governor on it at whatever rpm i was at. I would rev it real quick repeatedly, and it would do the same.

At lower rpms (and by that i mean only slightly over idle) it runs ok, sounds ok. But once it hits a certain rpm it just goes downhill rapidly from there. IF it was a leaky injector, wouldnt it have the problem thru ALL rpms, and not be ok at lower rpms? Because if so, i would be more likely to believe the fuel pump is my problem. (it also squeels very loudly, you can hear it from inside the car, outside, even standing in front of it while its running!) If not, it may be an injector.

I was also thinking it was a leaky injector because of how its backfiring, a bad/going bad fuel pump wouldnt cause the car to backfire, would it? I didnt think it could, but maybe im wrong.

I should also add that it didnt stall today, but it has before. Not sure thats noteworthy, but figured it didnt hurt to add that.

I have my battery unplugged right now and im going to go back out and run the codes again, maybe that'll help.

Thanks again for all the help guys.

Black88Z

Autozone has a fuel pressure test kit so im getting ready to go get that and check it, the fuel pressure should be 40-44psi correct? It doesnt make any difference if its warm/cold does it?

ahankins32984

the psi should be between 35 and 49psi i believe

Black88Z

i got the test kit but it got too dark for me to do it today, so ill do it tommarow. I did run the codes tho, i got 33, 36, and 51. Before i had more codes, so ive seemed to have cleared a few (hopefully).

This is what i found:

33. High voltage (low vacuum) at mass air flow sensor (or MAP sensor)

36. Burn off at mass air flow sensor OR Problem in transmission shift OR Fault in direct ignition system OR Missing pulses in electronic spark timing signal

51. PROM error

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Im not sure what the prom is or what it does to be honest. I didnt have that code before, but i had the other two.

Before i had another code and i was told sounded like it was my knock sensor was bad, and that probably caused the code 36 too.


ALSO, something i found very odd! When i reconnected the battery and started it, it started up and ran fine. The SES light came on, and me and my brother got in it getting ready to read the codes. i was letting it run for a bit, i know your supposed to let it idle for a while then rev it a little to get the computer up and going right again (so i was told.) Well after a couple of min of idling, i started to rev it just a little. I did this about 4 or 5 times, then i got on it a little more. After doing this maybe 3 times the SES light DISSAPEARED for maybe 5 seconds and then came back on! I revved it a bit higher, probably to around 3k while the light was gone and the car was PERFECT! it ran spot on! I couldnt believe it, and i didnt really know what to do because i was so thrown off lol. Well it came back, and although its not 100% like it temporarily was, its (knock on wood!!!) better than before. So of course now im completely confused about this!

ahankins32984

I would clean the MAF the PROM is the computer chip its in the ECM

Black88Z

Ive cleaned it before, maybe 2-3 weeks ago. I guess it doesnt hurt to try again, but im not really sure thats it. I was told that the code might be because the computer called for a burn off but it never actually happened, so i thought that may have been it.

What could be wrong with the prom? Is it possible to have just a random, inconsistent error with it, throwing a code but not having a real problem with it?

Black88Z

Also, if im going to check the fuel pressure tommarow i need to take the fuse out for the fuel pump. Is the fuse for the fuel pump on this fuse box? This is the one by the drivers door:



Is it the one 2 to the right and 3 down? It says "F/P Injct2". Im not sure what Injct2 means, i figured it was probably the passengers side injectors' wire harness. I thought the F/P was probably Fuel Pump, but i thought i should verify this before pulling random fuses.

Black88Z

I went out to start my car earlier and it started ok, idled fine, and after a few min of warming up i started revving it a little. Not much probably around 2k or so. It did ok the first few times, then it stalled after i revved it again. I thought it was odd, and right as i was going to start it again, the SES light just kept repeatedly flashing once and the box i have pictured below was making a ticking noise, like that of a relay. i tried running the codes like this and it just kept flashing once over and over again. I started it and it ran fine. I still have the same problems, but it didnt stall right after start up or anything again. I wasnt sure what to make of this. I dont know what the box is, so i took a picture of it, its below:




Im working on check fuel pressure and ohming the injectors now.

Thanks again everyone

Black88Z

Ok, well the car is running like absolute S**T now. Idk whats wrong with this thing. It hardly idles, it sounds like its going to die at any second and it has stalled multiple times while idling. The battery volts gauge says at idle it has anywhere from 9-12V, it usually is close to 10 but fluctuates around there. Before it always had 13-14.

BUT, if you push the throttle in even just a little bit,it smooths right out and the battery goes right up to 13. I ran the codes again and got:


23 Low temperature at manifold air temperature sensor OR Throttle position sensor error

33 High voltage (low vacuum) at mass air flow sensor (or MAP sensor)

36 Burn off at mass air flow sensor OR Problem in transmission shift OR Fault in direct ignition system OR Missing pulses in electronic spark timing signal

42 Fault at electronic spark timing circuit OR Fault at direct ignition system OR Fault at fuel cutoff relay circuit

51 PROM error


To me this sounds like a TPS error, but i know that its set correctly, i even double-checked it. .54V. I dont know where the MAT is, so i cant unplug it to test that.

Before this happened i had all the codes BUT 23 and 42, so im sure its related to one of those.

It didnt do this until i plugged the battery in and started it to run the codes. I didnt realize i left the paperclip in the scanner part,and the check engine light started flashing. But i read somewhere that you could do that, so i dont think i did any damage there. But right after i realized it was still there i shut it off, took it out, started it again and it ran like crap.

Black88Z

I ohmed out all my injectors and theyr all fine, all at 17 and within .5 of each other. As realiving as it is to learn this, its also frustrating because i still dont know what my problem is. But, i do know that my injectors are not the problem.

I was not able to check the fuel pressure today because of how poorly it was running for a majority of the day. Ill try to now, but its getting dark fast so it might have to wait until tommarow.





Ok, i have a hypothetic question for you guys lol. My gas tank apparently leaks a little, it always smelled like gas from the back of the car, and i had the car parked on a hill facing up, and i noticed after a few days there was a "small" puddle (well, its diameter was a little wider than my size 10 shoe) of gas on the ground under the gas tank. Thats quite a bit of gas, so im not sure id even consider that a small leak.

Is it possible that the leak is causing me to not have high enough fuel pressure?? I noticed when i took the gas cap off nothing happened, no pressure was built up at all! And it kinda would make sense, the car runs richer when its in closed loop, and the warmer the car gets the worse it runs. But im not entirely sure because like i said before, when the check engine light momentarily dissappeared it ran much much better. Its also momentarily dissappeared a few times since then.

I should also mention that it seems to take longer for the car to start sputtering, missing, backfiring and/or stalling when it has a full tank of gas than when its got a half tank, ect. Right now its probably got anywhere from 1/4-1/2 and its worse than when it was full. Not sure thats why, but i figured it was worth mentioning. When the tank is full its probably able to hold more pressure than when its half full or so.

Im going to take the shield off the tank and take a look, hopefully ill find the small hole/crack and be able to fix it without any problems. I plan to just patch it up with JBWELD.

Does that sound like it could be my problem?

midias

Whats the weather like? I had a friend who got a lot of water in his gas from a hole in his tank made his car run like ****.

305sbc

iTrader: (3)

It sounds to me like you have a loose wire, - possibly a fusable link going down to your starter.
Has anything been done to your starter in the time period where this problem began happening?
When some people remove the starter they let it hang by the wires, and that can easily damage the wires with the fusable links. After years of service and cooking from exhaust heat the copper strands inside get very brittle and can break on the inside, even though they look ok on the outside (insulation). This can cause voltage fluctuations and intermittent problems that will throw a variety of DTC codes.
Since revving the engine (engine block torquing over), and heat both affect damaged or loose wires, that leads me to think this may be your problem.
Also you said that you get a low voltage reading sometimes on your gauge.

The power feed from your alternator normally also connects down at your starter where the fusable links connect.
Another common problem down there is that many people will over-tighten the nut that holds the wires (fusable links) to the copper stud on the starter. Copper is very soft and often gets stripped if overtightened. In most cases of this you have to replace the starter. A better way to tighten the wires on is to use a combination of flat-washer and split-ring lock washer under the retaining nut so the nut can be locked into place without excessive torquing.

FYI, the power that drives your fuel pump also comes from the wires that connect at the starter. Intermittent problems there can have the same cause.

Black88Z

Hey, im in charlotte, NC, the weather has been in the upper 50's-mid 60's until just a few days ago when it dropped off to about 30ish on average. It hasnt really rained much either. The ttops leak, but i dont that really affects it lol. Im dont really think thats it though, i suppose its possible. Its had this problem for a while, so i think its more of a physical problem, not just water in the tank. ill put some treatment in though, who knows, maybe it'll help.

Black88Z

Nobody has touched the starter, and i havent had any problems with it either. I was wondering if the alternator was the problem, i didnt think it seemed like a battery problem, but i could see it being the alternator. Thats good info tho, ill remember that for sure.

Luckly, and i dont know how, but its gone now. Im not having that problem anymore. It starts fine, idles fine, and runs ok until you romp on it or it warms up. Its basically back to how it was this morning.

I talked to a mechanic (i gave him the short story tho) and he said he very strongly believes its the leak in the fuel tank thats causing my problem. He said it cant build up the pressure needed, and its leaning out the mixture. He said the fuel pump may even be sucking in air when i romp on it, causing it to bog down the way it does. Once i told him there was a leak in the tank he literally was able to tell ME the symptoms of MY car before i even told him what was going on with it.

I bought some water remover/injector cleaner and some JB WELD, tommarow ill take the shield off and look around for any cracks on the tank.

myzblubyu

Also, check all your grounds including the main set attached to the rear of your passenger side head.

ahankins32984

I can honestly say i would listen to myzblubyu his sons and him are the ones that found the problem with my 86 z28 and they got her back on the road for me!!!

Black88Z

Ok, ill double check them tommarow.

ive got a quick question, i was looking everything over today and i noticed that on the back on the manifold, on hte bottom, theres a connector thats not plugged in. Im guessing its a sensor, i think its either MAT or MAP but im not sure. Can anyone tell me what it is? i wasnt able to plug it back in, my hands are to big to fit in there. But im just curious of what it is.

305sbc

iTrader: (3)

You may have multiple problems. Can you post a picture of what you're talking about?

An 88 Irocz doesn't normally have a MAP sensor unless it was converted to speed-density.
In the rear of the intake manifold there are connectors for MAT, the ignition, EGR solenoid & sensor, oil-pressure sender & switch, and sometimes for a cold-start injector on the driver-side.

Black88Z

Oh ok. Ill try to get a picture of it tommorow, its too dark to now. Im not sure if my oil pressure gauge works, so maybe thats it.

These are the codes i have, but the only one that makes sense for it to me is 23.


23 Low temperature at manifold air temperature sensor OR Throttle position sensor error

33 High voltage (low vacuum) at mass air flow sensor (or MAP sensor)

36 Burn off at mass air flow sensor OR Problem in transmission shift OR Fault in direct ignition system OR Missing pulses in electronic spark timing signal

42 Fault at electronic spark timing circuit OR Fault at direct ignition system OR Fault at fuel cutoff relay circuit

51 PROM error


51 seems to come and go, i just got this one for the first time about 2 days ago. 42 isnt a usual one either, i got that right after it started running real crappy. Its running ok now (back to how it was anyway) so that code hopefully was just an intermittent thing.

33 and 36 i figure are probably related, both having something to do with the MAF.

305sbc

iTrader: (3)

I've seen code 51 pop up if the chip gets loose in the socket.
By that I mean that one of the chip pins may have a bad connection with its socket.

With a loose connection like that it can spawn many other codes to pop up falsely.

If the ECM isn't getting a solid power or ground it is possible for the code 51 to come up as well.

rusty vango

TPI parts.net has PROMS for our cars.also try hawks third generation,they have ecms for our cars as well

Black88Z

Sorry to bring up an old thread, but is it possible for a knock sensor to cause my problem?
(No, i still havent fixed it, its sitting at my dads shop not being touched)

Or is it possible the fuel tank leak is causing me to lose pressure, causing it to bog down like it does?

SKELITOR117

iTrader: (3)

Oh man! Did you get bone cancer?

305sbc

iTrader: (3)

That would be very easily determined by simply unplugging your knock sensor to test.
A fuel leak might, depending on exactly where the fuel is leaking from.

Black88Z

SKELITOR117- lol

305sbc: ill give that a try. The knock sensor has a PROM backup for it? I guess i didnt know that, i thought if i unplugged it it would be worse.

GreenCamaro13

lol

Black88Z

Alright, so ive got a question for you guys.

My car is at my grandfathers shop right now, waiting to be worked on. One of the guys there found some time to mess with it and plugged in a sensor that was unplugged. it was on the bottom of the plenum (350tpi), towards the back. I noticed before i had code 23, i reset the codes and 23 is gone. So i would just like to confirm that that sensor IS the MAT sensor?

Also, would the MAT being unplugged affect how the car runs? I read a thread on it but it was just a bunch of people arguing, no real help. Hopefully i dont get my head chewed off for asking xD

He also said he checked the fuel pressure, 30psi at idle, then dropped to ZERO when given any throttle. So im having the fuel pump replaced, ill probably have all the lines replaced, and the tank cleaned out.

88blackiroc

iTrader: (1)

II had a problem before with my iroc when it had a 350tpi and when cold and sometimes warm it ran like absolute crap. Ses light blinked rapidly and car idled real funny and did not want to rev. Couldn't figure out what it was so we took it to a shop and the computer turned out to be bad. Not sure if its like your problem but something to think about!

Black88Z

Well i dont really think thats it, its not giving me any codes for ecm or prom, and my ses light stays on. The only codes i have now are 33 and 36, and i took a closer look at the connector that pulgs into the maf and i noticed its messed up. So ill replace that and heopefully the codes will go away.

Im sure that after replacing the fuel pump that will make the biggest difference, but does the MAT sensor aid in how the car runs at all? Because with it unplugged it would bog down, sputter, stall, and with it plugged in it didnt bog down or stall, but sputtered a very little. (didnt actually drive it though, only revved it in park. But before it would still have those symptoms in park as well)