ok i have an 88 iroc with a 350 tpi. i have been chasing a running problem and i dont really know where to start. i dont have the money to just throw parts at it. i have replaced the tps, iac, maf, maf burnoff rely. i checked my timing and it is at 6 degrees btdc. i got my injectors clean and flowmatched. the problem remains. the problem is irratic idle, horrible off idel hesitation, studders/stumbles under full load, NO CODES put on an occiloscope and the ignition system checks out pretty good. what do you guys think i should look for first? fuel ? any suggestions would help thanks guys remember im poor

 

Just asking, you did plugs/wires and cap/rotor right?

 

Did this start like 'all-of-a-sudden'? I had the same problemslast October. On visual inspection, everything looked fine, until I checked every inch of my plug wires and found 1 which was burned through by getting too close to the manifold.

Start there. But same thing like shudder/stumble and rough idle and horrible performance. Like the above post, if your plug wires all look good, check your plugs themselves. Maybe they were not gapped correctly or are just in need of replacement.

Both these are driveway jobs. You can buy single plug wires if one is bad at local parts stores. Pack of 8 spark plugs is maybe $10 plus cost of spark plug socket.

 

you should move your timming back up a little, maybe to 0*(TDC). You can give that a try.

 

6* I beleive is factory, retarding the timing would make an already hard to find problem harder to find. Seems like if there are no codes being thrown at the ECM then there is a possible vac leak somewhere, somehow. I would check every vac line and replace any that are in doubt.

 

i just had my car on the occiloscope and everything checked out fine but your right a wire could have fallen onto the manifold and burned through. ill keep you guys posted with the situation. and i set the timing at 6 degrees to keep it all factory. oh and this problem is wierd. every once in a while i would start to notice it start to "buck" a little but by the time i noticed it it went away. at idle and right off idle it was never as responsive as it should be. not like an efi should be. the person i got the car from has nearly everything capped off, pluged up, disconected, or removed. it sucks i want to just rip that **** off and start with a new aftermarket efi! grrr

 

 

i agree with the vaccum leak theory

you had your injectors cleaned and balanced

my quesiton is there it is very easy to put the tpi together wrong....

take some carb clener and go inside and around all intake parts see if you notice a difference....

and what was the torque/tightening sequence for the runners/plenium

 

i would be concerned about a vacum leak but the problem has worsened now the cart wont even start! it willl sputter but not start. if you spray starting fluid in there it wil fire up and then run for a sec then die. i believe its the fuel pump. a trick i was taught was to use a rag and compressed air and hold it around the filler neck to pressurize the gas to force it up to the lines. i did this and the car would start and run but as soon as i pulled the compressed air nozzle out it sputtered and died. would anyone argee that my diagnosis is correct?

 

Throw a fuel pressure gauge on it and see if you're getting any pressure.

 

My 88 5.7 shows 8* on the sticker under the hood.

 

i went to do this today i put the gauge on to see pressure and nowe the pump wont even kick on. its been doing this for a while it will somtimes run too long and not shut off and sometimes it wont kick on. is it possible for a relay to not kick on? if the contacts are corroded? also if this is possible, could it be thatv the relays corrosion was a big retriction ( voltage wise) and therfore the pump was not getting the proper voltage and not pumping sufficiently? wierd my 88 350 shows 6 degrees. by the way do you guys run for initial timing? what are the benifits and not so benifical aspects of incresing initial timing? i was rweading in a hot rod mag that " 6 degrees of intial timing is stock but f-body guys know 12-15 is better" ? any thoughts
?

 

test your fuel pump w/ the ALDL... IIRC it goes through the fuse and then right to turn the fuel pump on.

 

so your saying to bridge the G and A terminals with the key on to see if it will run? just like you bridge the A and B terminals to pull codes?

 

correct

 

alright ill give her a try tonight. i got a spare relay thats good so ill try that as well

 

Mine did the same thing yours did a few years ago. It ended up being the fuel pump.

I would get a fuel pressure checker and see what PSI you are running.

 

Small thing but I didn't notice you saying that you had replaced the fuel filter.

Your compressed air test sounds interesting, but a surefire way to check is to monitor the fuel pressure. Just make sure that fuel filter is good first.

If the fuel pump doesn't cycle, you can also find a fuse and connector on the way back near your battery and above your differential to check for power.

Don't overlook ignition problems. In my experience starting fluid is easier to ignite than gasoline and even a weak spark can get the car started with a shot of hexane or whatever they put in that spray can. I'd verify that the fuel pump is working before straying elsewhere, though.

 

ok sorry for no replys for a while. heres what i found so far. a bad fuseable link near battery, a bad in line fuse near the battery stripped wire to the relay itself. now that the fuel pump runs and shuts off properly i will further my search. i have 10 psi on the rail instead of 42 like it should. the pump is not drawing enough amperage at 2.4 amps it should be more like 4 amps. i have futher electrical testing to do ill let you guys know the results.

 

bump

 

i feel dumb i see people say bump all the time what the hell does that mean? got my car running better but it still has a horrible tip-in throttle responce.