View Full Version : serious problem and no one can figure it out.


romanianfury
04-21-2012, 04:23 PM
First off let me say I have been a long time member of ltxtech and have exhausted all the advice from the forum members there; so I decided to come here and broaden my horizons in my reach for help. I really hope there is someone here that can help me figure this problem out. Thank you all in advance. And before anyone flames me, i did put a scanner on it and it said that the computer was not responding. I will list the story below and ive uploaded a video of the problem.

Story:

car is a 1994 camaro z28 m6. odometer reads 234,000 miles on it. was told by previous owner that the motor had been replaced. about three months ago i replaced the opti spark, water pump, and wires. checked the plugs and they were a bit black but i ran out of money so i kept em in. now on to the problems. the car seems to stumble throughout the entire rpm range. its not a misfire or a pop but more like hesitation. This happens regardless of throttle input. the stumble is similar to when someone lets out the clutch too soon in 1st and it jerks. now, when the car is at full operating temps and idles, it holds 20psi oil pressure or so but starts to bounce around up and down. ok update time. i checked and had one of the wires unplugged. put that back on and tested fuel pressure. with the key in "on" position, the fuel pressure read 38psi. with engine on idling it read 39-40psi. when the engine turned off it read around 30psi and fell very slowly. it still seems like the idle is weird, choppy, and weak. then at times the car turns over but won't start, during this time fuel pressure reads zero at shredder valve.

youtube;NL1sBilhpR8]http://www.youtube.com/watch?v=NL1sBilhpR8

mantycarguy
04-21-2012, 06:45 PM
Sounds like a possible ignition switch problem.

1ltcap
04-21-2012, 06:51 PM
have you checked fuel quality?

romanianfury
04-21-2012, 09:46 PM
the fuel quality was not good at all. the tank was low and sat for a while. I changed the fuel filter and ran a bottle of seafoam through it and put in 7 gallons of fresh premium. You can tell in the video how the car is running like crap. I listed the story of what is going on, has nobody had these symptoms before?

89 formula350
04-21-2012, 11:24 PM
you need to find out why you cant pull codes with the scan tool.

no fuel pressure at times? how long does this last?

check your pcm connectors for indication of water damage. then maybe tap the pcm fairly hard with a screw driver handle (not trying to damage the case but a good solid vibration to see if there is a change in its operation)

1ltcap
04-22-2012, 01:24 AM
the fuel quality was not good at all. the tank was low and sat for a while. I changed the fuel filter and ran a bottle of seafoam through it and put in 7 gallons of fresh premium. You can tell in the video how the car is running like crap. I listed the story of what is going on, has nobody had these symptoms before?

the last time i saw what you're describing, i took nearly 4 gallons of water out of the tank.

Old Geezer
04-22-2012, 08:52 AM
"then at times the car turns over but won't start, during this time fuel pressure reads zero at shredder valve."


Do you have a tach signal when this zero psi issue is present??

romanianfury
04-22-2012, 02:33 PM
I will try tapping the PCM and see if that does anything. It is very strange the PCM was not responding to the scanner, although I'm not sure if it was my PCM or the universal obd1 gm clip that came with the scanner. I have had the stumble problem for a while now, it just got progressively worse over time. I might add that the car sat for 2 weeks, I changed the fuel filter and the fuel coming out of it was rusty brown. Afterwards, when I checked the fuel pressure at the valve, the fuel was golding colored. When the car doesn't start and reads no fuel psi, the car just keeps turning over quickly with no start. Usually if the car sits a couple hours it fires back up.

1ltcap
04-22-2012, 04:47 PM
I will try tapping the PCM and see if that does anything. It is very strange the PCM was not responding to the scanner, although I'm not sure if it was my PCM or the universal obd1 gm clip that came with the scanner. I have had the stumble problem for a while now, it just got progressively worse over time. I might add that the car sat for 2 weeks, I changed the fuel filter and the fuel coming out of it was rusty brown. Afterwards, when I checked the fuel pressure at the valve, the fuel was golding colored. When the car doesn't start and reads no fuel psi, the car just keeps turning over quickly with no start. Usually if the car sits a couple hours it fires back up.

if you're still obd1, with the old style gm connector........use a paperclip in the upper right hand pins of that connector. when you jump those, and turn the key on, the CEL should flash any codes.

mantycarguy
04-22-2012, 07:27 PM
You need to confirm both bat+ input and key on input to your pcm.Usually with a no or marginal battery input to the pcm you will not be able to communicate the scan tool. You will need to find the pinouts for your specific model and verify fuses and connections to the pcm. Also verify all grounds as any circuit is only as good as the grounds.

fastassls1maro
04-22-2012, 07:44 PM
could be a weak fuel pump with 230k miles on it? it may have good pressure but not enough flow. I would be curious if it were ever changed? Also the fact you said there was brownish fuel coming out when you changed the filter could be also clogging up the fuel pump screen

2 Stroke Racer
04-22-2012, 08:39 PM
I wouldn't rule out opti-spark. I've seen new ones fail almost instantly.

romanianfury
04-23-2012, 01:55 PM
will be doing tests this week to see whats going on. I know its not the optispark as i am getting really good spark at all times. the problem got worse when i changed the fuel filter and put in a can of seafoam

Old Geezer
04-23-2012, 02:01 PM
1. Rusty fuel in the tank is a good way to ruin the pump.
2. Seafoam can/will wash the $hit off the tank and into the pump sock, causing low/no FP.
3. The $hit may well have been pumped into the injs, since you say the filter was full of it.


Time to clean the entire fuel system, replace the pump, filter. and clean the injs.

romanianfury
04-23-2012, 02:05 PM
how does one clean the fuel lines?

MikeyZ
04-24-2012, 02:19 AM
Sounds like the maf and a bad/failing fuel pump or wiring/relay

romanianfury
04-24-2012, 09:31 AM
There is actually no change in how the car runs when I unplug the maf. I will be dropping the tank and cleaning it, blowing out fuel lines, putting a new fuel filter, and inspecting the ignition components this week. I will keep this thread updated so maybe others with similar problems can get some advice. Thanks to everyone who's chimed in so far. Is there an easy way or a write up on how to drop the tank?

Old Geezer
04-24-2012, 04:22 PM
Look CLOSELY at/in the ends of the lines. Look for signs of rust. if there is, they are JUNK....