Hi Everyone;
I just joined because I'm at my wits end with this and am tired of buying parts and wasting money to find out its not fixing my problem. This is an 89 IROC with the TBI 305. This problem started, all of a sudden, it was not gradual. What it does is massive surging at idle (down to about 200 rpms up to about 1200 rpms) and try as I might it is nearly impossible to get the RPM's above 2000. It just won't happen. The car is not misfiring or backfiring at all. Here is ALL the things I've done:

1. Put fuel stuff in the car to evaporate out extra water thinking it was a bought of bad gas.
2. Fuel injectors are new - only have about 500 miles on them
3. TPS sensor replaced
4. EGR replaced
5. IAC replaced
6. O2 sensor replaced
7. Checked fuel pressure, its fine
8. Checked all vacuum lines - no leaks

When I was killing myself to get it home (which let me tell ya was a challenge) it spit out a code 44 lean condition. Although it was obvious by the smell of the exhaust. However, since I've unplugged the battery three times now to reset the system, I've not received this code back. No other codes exist. I'm considering replacing the MAP sensor and someone told me perhaps the ignition module is going bad and not keeping dwell right but in my experience when those fail they just fail - they don't intermittently work.

If I unplug the TPS the surging remains but at least it doesn't die. If I leave the TPS plugged in it will eventually die on its own. I'm also thinking it may be a bad ECM since I have no other trouble codes. Any thoughts on this would be really appreciated because I don't know what else it could be.
Thanks,
Dawn

 

Have you checked your base ignition timing (with timing wire unplugged)? One possibility that jumps to mind is a timing chain that's jumped a tooth. This will be obvious if you check the ignition timing as it will be retarded about 16-18* from where it should be. Bumping the timing back up (0* is stock setting for a TBI engine) will get it running a bit better, but it won't fix the core problem (the timing chain needs to be replaced).

Not saying this IS the problem, just a possibility to rule out.

 

When you checked the fuel pressure what did you record? Sounds like you have a dying fuel pump. An LO3 can "kinda" run on a dying pump producing only 4 to 7 psi. 9+PSI is needed to assume the pump is working to capacity.

 

I'm pretty certain its not a jumped timing. I've experienced that before and that wouldn't cause the surging I'm getting. And, if I pour carb cleaner down the TBI while its running it clears up like a kitten and runs great. There is no timing mark on this car since the timing is computer controlled.... how do you check it?

Yes, I haven't hooked up an actual fuel pressure gauge and have read that a dying pump can cause this problem. I just did the "unconnect and turn the key on" test and gas SPEWED out like crazy. So, that is a good suggestion and I will do that before buying more parts. It could be dying. I replaced it once at around 100,000 miles and the car has 180,000 on it now. I hope that isn't it.... really don't feel like dropping the rear end to replace!!!

 

You have to get over the top of the water pump and look nearly straight down to see the timing mark.

Although the timing is computer controlled, the base timing is still set by turning the distributor.

 

Which probably means it is starved for fuel and runs normal when you directly add "fuel based" substances into the motor . I would bet the farm that your pump is dying. Might be time to get a TPI or walbro pump. You can rent a fuel pressure tester from AutoZone for free if you want to get an exact reading for validation.

 

I agree with Shifty's opinion too. I had all the same symptoms as you a while back with my LO3. It turned out to be the fuel pump. But, just to be sure, get a gauge hooked up check the pressure. Good luck!

 

Clogged fuel filter? Has that been changed?

 

I will be changing that again tomorrow even though it only has 4000 miles on the filter. The pressure gauge I had didn't work so I'll have to go out and buy one of those just to see if its the problem. I absolutely LOATH working with fuel.... its so bad on the skin (and being a woman I'm a bit more concerned about that) but I must suck it up and fix this. I've been fiddling with this car for three weeks and am TIRED OF IT!
Thanks,
Dawn

 

You can verify if you have fuel delivery problem by pinching off return fuel line - find a flexible section of fuel return line (passenger side of the TBI) and gently pinch it with pliers wrapped in a towel. Do not attempt to pinch solid tubing!
If the idle improves you may have a broken fuel pressure regulator spring. It is an easy fix, but it still requires getting hands dirty. There no ways about it.

//RF

 

Oooo!! Cool!!! Something new to try and I don't know why I didn't think of that! THANKS!! I'll try that first thing!!!!!!!!!!!!

 

I have a 91 with the same problem. Let me know what happens. I would like to set it on fire if I hadn't put a new motor in it. I have replaced every sensor because I got a code for them all at one point or another. The fuel pump or the regulator has to be my problem.

 

Well, replaced the fuel regulator - no change. I'm not completely convinced its either a dying fuel pump or a clogged sock that goes onto the end of the fuel pump. This fuel pump has about 80,000 miles on it so its a good possibility... its just a pain in the you know what to change on this car........ I'll keep you all posted.

 

I would rent a fuel pressure tester to remove all doubt. This wil prevent you from just throwing parts at the car which will cost you more in the end.

 

I had the same problem. Was not the fuel pump, but the 2" section of rubber hose that connects the fuel pump to the hard line of the gas pick up unit. Seeing that these have been partially submersed in fuel for 15+ years, they become soft. Mine had a split which made the majority of the fuel just pump back into the tank.

Might as well upgrade to a better pump since you need to drop the tank. Since it is an AZ car like mine was/is, it should not be that bad of a job. Just drain all the fuel out. I jumped the fuel pump relay to run the pump constantly and drained the gas into a can using an extension hose off the engine bay fuel line.

 

Well it would be nice if she'd reply and say if she fixed it or not . Especially since I have a similar problem on my 92 Bird .

 

I had the same problem that graebz28 had... the little rubber hose had just turned to sludge... I replaced it with a new piece with a crapload of zip-ties around it to give it some more strength

major PITA to drop the tank though...

 

Well I'm having similar problems , surging idle and hesitaition on small amount of throttle , but good on the highway , on my 92 305 TBI , but when I look at my tank area I can see 4 rubber hoses all running up to the pump area and all 4 are in good shape . Is there actually more hoses , or different ones on top that you can't see until you drop the tank ?

 

Hi Everyone;
I neglected to post ultimately what the problem was - sorry about that everyone!!! All that money spent on new sensors and crap for naught. There was a split in the small hose that goes to the fuel pump in the gas tank. That is why it was reading a lead condition the whole time - couldn't cyphon enough fuel. So I had to drop the tank and all... ended up putting a new fuel pump in it while I had the whole thing apart. After that, she ran like a charm.................