TopdownIroc

Ok guys need some help.

My car is running very rich to the point that yesterday it was blowing raw fuel when I gassed on it. I even had to resort to the flood mode to get it started. Its a stock 305 TPI with no mods other than headers, smog delete (EGR still intact), Hooker off road Y pipe, and flowmaster cat back. The car sat for about 3 years, but was fired off weekly and left to warm up. When I relocated from one house to my new house I noticed it was running really rich and was exhibiting long start up times. This was when it still had a cat, manifolds, and AIR. It stinks no more now with the ORY than with the cat and full smog equipment. Tonight I got a wild hair and decided that I was going to seafoam it and see if it made a difference. I'm not one for chemical cures, but I am at my whits end. I seafoamed the intake and it smoked like the garage was on fire, shut it off for five minutes then refired it. It exhibited better throttle response and ran smoother than before, so I put the stuff in the tank as well. Also the car would start faster than before and does not need to be put into flood mode before key turn. I ran a quarter tank of fuel through it at various RPM when all the sudden holding at 2000 RPM it developed a miss that seems to be getting steadily worse . It only misses when held at constant RPMs or when its idling in gear. It revs out great. I have chased many things to try and find the problem and all to no avail. Maybe you guys can help . Here is my list of things I have tried.

1. Ohm out the CTS with .929k ohm results (in spec for temp)
2. Installed new primary coil
3. New plugs prior to what I believe are fouled now
4. Checked for injector power (have 12.5 on all pins with key on)
5. Tried to pull codes from ECM (code 12 only no others)
6. Pulled wire from MAP while running (idled down and appeared that the computer compensated and kept it running)
7. Used carb cleaner and checked for vacuum leaks (none found)
8. ECM reset
9. Fuel pressure test (40 psi on prime, 38-39 psi while running, 20 minute leak down time after shutting off engine and losing all 40 psi at the rail)
10. FPR checked for fuel in vacuum hose (none)
11. FPR vacuum pulled while running (pressure went from 40 to 45 psi.)
12. New MSD wires when headers were installed (no crosstalk or opens)
13. Full range of throttle response (excellent so I figure the TPS is good)
14. Listened for the IAC to respond to varying conditions (works great and idles down perfectly from cold start)
15. Listened with a stethescope for injector clicking (all is well)
16. Ohm out injectors (not all are great but here are the results 12.1 15.6 16.1 14.8 16 16.4 16.2 12.8, also not sure what is in spec anyway)

So here are some questions I have.

1. Could this result from an injector hung open and still not cause a drivability issue?
2. Would an O2 cause this rich of a condition without throwing a code?
3. Could the injectors that may have been stuck open be clearing out and the plugs have just fouled so bad they cant fire a proper mixture?
4. Could the injectors just be taking a dump all together because there was no miss at all prior to seafoam?
5. Could the carbon release from the seafoam in the intake have just fouled the plugs like I figured it may?
6. Could the EGR do this even though there are no codes?

Anything you guys can come up with will be greatly appreciated!

Eagle223usa

The injectors should all check out at 16.5 (new) I think... I've also heard that a bad MAF sensor (85 to 89 cars) can cause it to run rich without throwing a code. That happened to my 88 L98 back in the day when Chevy still serviced them. Just noticed your car is a 90, I never owned a SD car.

TopdownIroc

I myself have never had experience with any EFI prior to this one. I've had the car for 11 years, but this is the first time I have had any issues with it. I am leaning heavily toward the injectors being varnished. I guess my best bet is to throw them in the dumpster and get me a new set. If your resistance figures are correct, it tells me I have a few that are just too far out of spec. Thanks for your reply!

TopdownIroc

So onto the next step. I have heard that you can run Mustang yellow top injectors in the TPI. If this is true, what is the fitment like? Are they the same height? Do they have the same harness plug in? I am also to understand that they are 19 psi. at almost the same running pressure of the standard multech injectors. Any ideas?

southbay08

you are correct, you can definitely run the yellow tops in the tpi. They are 19lb at 43.5psi. They have the correct electrical connector for your application (ev1 / jetronic). As far as fitment is concerned they fit just fine. They are not like the bosch lll's because you have the ability to use the clips for the rail,,, the bosch lll's do not use clips so to have them fit properly you need to either use a double oring set up or our adapter.

TopdownIroc

Your an injector guy, so compare the two injectors for me. Which is better and why? I know I can get a set of yellow tips for $80. Will I need to raise my psi to run them since my car runs at 38 psi idle, or is it the off idle when it jumps to 45 psi that makes the difference; thus the vacuum reference.

southbay08

The yellow top injectors are one generation older than the bosch lll's. Both are fine injectors, however the bosch lll's are one of the newest design injectors and they have a more improved spray pattern with better fuel atomization. As long as the injectors that you are interested in for $80 are cleaned and flowtested then there is absolutely no reason why you cannot use them for your application. 19lb injectors are the stock replacements for the 305's

TopdownIroc

Thank you for all the information. I guess when I can afford it "this is not my daily driver, just a toy" I'll call you guys up and get me a set of the Bosch III. Assuming they are a direct fit injector.

southbay08

No problem, if we can help you with anything please do not hesitate to contact us!

TopdownIroc

Do you guys still offer a discount to thirdgen.org members?

southbay08

we sure do....10% off. If you decide to make a purchase and you go through our website just type in promo code tg11 at checkout. Otherwise you can give us a call.

TopdownIroc

Thanks so much.

TopdownIroc

Ok, got some seemingly new problems now. I have not messed witht the car in a week or so. I went to start it up yesterday to get it the hell outta my way and what do ya' know... I had to fuel it through the throttle body to get it to fire. It started like a brand new car. If the injectors are dumping too much fuel and I was having to use the flood parameter to start it, why is it that I now have to fuel it manually to get it to start? It runs great after I fuel it. My pressures are good, I just don't get it. How can it run so fat and not fuel itself enough to start? So tonight I went out and just turned the key and it spun for 20 seconds then popped and sputtered. It finally came to life. Any ideas?

TopdownIroc

One more thing to add. This sounds stupid, but do any of you all think that my fuel filter could be blocked? This in turn causing the ecm to compensate by running it rich due to lack of volume vs. pressure. Just a thought I had.

darrelldta

Mine was running so rich it was burning out my cats. Changed the temp sensor and fixed the problem. Ecu thought it was -120 outside.

TopdownIroc

Ripped the intake off yesterday. I'm gonna put new injectors in it and change the CTS, IAT, EGR, and FPR while I'm at it. The stuffs almost 22 years old so I'll just do it while I've got it down. Hopefully that will fix the issue. If not I might build some kind of homemade incendiary device and give the damn thing hell.

TopdownIroc

Oh yes, one more thing. I put paper towels under injectors before removing the rail. I pressured the system and had no dripping or leaking. Is it possible that the injectors are not hung open, but do so when the car is running?

skibum2100

Have you considered upgrading to a heated 3- or 4-wire oxygen sensor?

TopdownIroc

I have considered the three or four wire O2 if for nothing more than tuning alone. I think when I replace the factory one that I'll go ahead and do that. I have read that if the O2 is too far away from the heads it can read false due to less heat build up. Not to mention I have an ORY car so that alone could cause this. A self heating O2 would definitely remedy that issue.

mechanic58

I have an '87 IROC with a VIN "F" 305 in it that is doing this same exact thing. Like the OP's car, it has been sitting up for over a year. It runs well at WOT and part throttle, albeit still very rich. However it runs so rich at idle and lower speeds that it barely runs. I have checked the coolant temp sensor and it checks good across all temp ranges. Subscribing to this thread.

mechanic58

Been doing some troubleshooting on mine, I have two trouble codes, 21 & 33. 21 is for the TPS (high voltage) and 33 is for the MAF (high voltage). I'm kinda curious about why I would have both of these codes - makes me wonder if I got some bad wiring. The MAF just looks bad, the sealed cover that's on it is loose...so I feel like the MAF is probably the main culprit. I'm just wondering (also) if the fault its having is also causing a trouble code for the TPS.

TopdownIroc

Put a fuel pressure gauge on the rail and prime your pump. If the pressure bleeds off quickly then pull the plugs. If you find raw fuel on the plugs or on my case, it ran out of the cylinders, you need to pull the rail off and replace your injectors. Also check your FPR. When running pull off the vacuum line to the FPR and it should jump up 7-10 psi. Then again, it could have just a slight crack in it allowing it not to work properly. If that's the case I would smell the vacuum line and see if it stinks of raw fuel. If so; there is your answer. If you have luck like mine it will be the injectors suffering from varnish. Check Southbay. They will hook you up.

TopdownIroc

I would definitely check the pigtails. You never know what might have happened to the wiring while sitting for a year. The TPS for sure can do what your describing. I've had it happen to me before. Gotta remember how old these things are and that the sensors are wear parts as well. Also have you checked your CTS? As far as the MAF faulting the TPS, I just dont see it. They have two separate codes. But then again I am SD so I really don't know.

mechanic58

I am planning on checking the FPR as I have had that experience before myself, however I do not think that I have an injector problem. The car runs good at WOT and makes good even power. It runs extremely rich at idle, so much so that I have to block the throttle open so that it WILL idle...and it chugs black smoke until you clear it out. Its got high voltage at pin C on the MAF...so the ECM thinks there's high air flow....so it's making the mixture rich. I'm going to replace the MAF first.

I have checked the CTS through a wide range of temps, from ambient to operating temp, its working properly. That was my first order of business.

TopdownIroc

That being the case I would definately do the MAF. Ive heard they can do crazy things. The TPS can also do that not idling but run well mid to top end thing. I had one that I would have to warm up like a carb car because it wouldn't idle when started.

TopdownIroc

Well it seems I might be a total dumb***. I threw the TB back under the hood and hooked it up. I probed the center wire and ran my negative probe to ground. The TPS gave me .9 - 4.5 vdc. I know this is out of spec, but could this be my major issue? Car never stumbled or accelerated weird. Maybe the fuel system is ultimately not to blame? Any ideas?

mechanic58

The range should be more like .2v-4.9v. Is your throttle plate going all the way closed? Should be around .2v at idle.

TopdownIroc

Yes closed all the way. The intake is off the car. I just hooked up the throttle body and battery to test TPS. I thought low side should be .54 vdc.

87IROC-DAN61

Hello TopdownIroc!!

Yes, you are correct about the TPS spec, it's .54 VDC +/- .08 at fully closed throttle.



I was wondering if you did a fuel volume test, as you could have the right pressure, but not enough volume, which would lead me to suspect that your fuel pump is weak.

This in turn would cause havoc for the o2 sensor/ECM during closed loop operation in adjusting your short/long term fuel trim. Possibly biasing it to run rich.

Feel free to correct me on this theory!!

Remember, you did say that it sat for 3 years, original fuel pump........!!??

I'm chasing the same sort of thing as we speak, and that's my next step.



P.S. Southbay is top notch!!!!!

TopdownIroc

I mentioned this in another post and nobody replied. I'm glad someone else has thought of this as well. I am unsure of volume testing and how to perform it. I would assume unhooking the feed line to the filter and measuring volume somehow? And yes fuel pump is original. The question I have is that the ECM has nothing to do with it until closed loop (right?). I figured it would at least start with the rail pressure, but I have to prime it through the throttle body. But yes I have thought about that.

87IROC-DAN61

Hello TopdownIroc!!

Get yourself a fuel pressure gauge test kit, the one with a drain off hose, you can use this to test your fuel pump volume from the valve on the fuel rail!!

Go to youtube and search fuel pump volume testing on a fuel injected car, there are a few good ones there that show you how to do it!!



The ECM gets a signal from the o2 sensor once warmed up enough that it will start to control your fuel trim, switching back and forth from lean to rich, this is closed loop operation!!

However, the ECM/sensors can be bad and cause all types of problems!!

TopdownIroc

Ok, have come to the conclusion that though the injectors are not leaking, they are worn and varnished. Also I need a new FP. It's refusing to build more than 25 on prime even after a filter change. It bleeds off normally but it just doesn't get there. I guess the injectors can't atomize correctly under these conditions and have caused my rich exhaust. Damn I really hate having multiple things wrong with the same system of the car. It makes diagnosis kinda' difficult. Thanks 86iroc-Dan61 for bringing te volume issue back up. It seems a weak pump is 90% to blame for my issues. Now to rip the f'n third member out to replace it. Thanks all.

TopdownIroc

Well I finally got around to ordering my injectors. It took a damn long while. Thank you for offering the discount to TGO members, it helped a lot. I'll be looking forward to installing the new Bosch III units.

Eagle223usa

Good luck Brother, When you pick a fuel pump go with a good one like Federal Mogul.

TopdownIroc

My plans were for a Delco, but what would be your take on the Aeromotive in tank pump? I have heard great things about them, but would like some input from my fellow TGO members.

ninetyone

iTrader: (2)

injectors should all ohm-out to about the same ,all of mine are at .15

TopdownIroc

Just wanted to give everyone a big thank you for all the information. Turns out that the new injectors did indeed fix the issue (thanks Southbay). After setting base timing, IAC, base idle, and TPS, the things revs out better than ever before! Anyway, thank you all for your help.