A couple of weeks ago my car ran great, and I started it up on afternoon and it ran like crap. It is fine with very light throttle but any more than that it will run rough and sometimes cleans out at 4500 rpm and up. It runs almost exactly like when it had a bad cts but I checked it and there are no codes. I am thinking my new injectors got some dirt in them, is there any way I can see the spray pattern before I send them away to be cleaned. I really want to get this fixed soon, my new stage 3 pro-built tranny is in next week.

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86 Iroc, 383 Ported and polished Sportsman II, stock ported TPI, #24 svo, custom chip, Slp 1 3/4, Comp Cams roller 218 224, 10" 2600 stall, Fairbanks 700r-4 W/superflow pro pump, 12.969@106.54 1.991 60', new times in spring
87 K30 Chevy P/U 355 TPI Crane Compucam, Ported heads TH400, Hooker headers and edelbrock mufflers (LOUD)no cats, 8" lift, 36" super swampers, 4.10 detroit lockers,

 

I forgot to add, it has 27 degrees of advance at idle and doesn't change at all as I rev it up.

 

If you know your advance you must be in possession of a scan tool. With that in mind i'm not breaking my back guessing this problem, youy can watch all of your sensor/actuator data and look for what is wrong.
I'm not trying to be a *****, it's just why guess when the answer 'is' in front of you. If advance is staying constant then i would say one of your sensors must be completely shot but yor ECM's self diagnostics are too dumb to figure it out (what, a stupid OBD I computer, lol, what a concept, hehehe)
If everything is otherwise normal and in range then yes something funny like a clogged injector could cause your problem.
...ed

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Ed Maher - Moderator @ The TPI & Carb Boards
92 Z28 Convertible - Quasar blue / Tan top
LB9 4L60 GU2 G80 - stock, soon to be sleeper
-=ICON Motorsports=-

- Definitely prototypes, high powered mutants of some kind. Too weird to live, too cool to die

 

I don't have a scantool, I used a timing light with an advance dial.

 

Oh, sorry then. Checking your timing in neutral revving really isn;t telling you anything. I don't know exacty what is in the MAF computer, but advance may be staying constant simply becuase it is in neutral, or it could also be that it is staying constant b/c that is just the way your spark curve is in the no load area.

So basically, i'd check the TPS and the CTS with a DVM and make sure they are giving reasonable values. Other than that, a bad MAF could also do what you are describing, and for that matter it could even be something getting weak in the ignition.
...ed

 

Last night I took the plenum off and turned the fuel rail over and cranked the engine. The injectors all sprayed the same, so I think they should all be fine, and they were all around 14 ohms. I already replaced the cts, tps is good .55 closed 4.5 wot. One wierd thing turn on the key and my autometer air/fuel gauge reads stoich which is 14.7 to 1 without even starting the engine. I would think it would be down at rich because the engine is cold. I also tried a new ecm, no luck.

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86 Iroc, 383 Ported and polished Sportsman II, stock ported TPI, #24 svo, custom chip, Slp 1 3/4, Comp Cams roller 218 224, 10" 2600 stall, Fairbanks 700r-4 W/superflow pro pump, 12.969@106.54 1.991 60', new times in spring
87 K30 Chevy P/U 355 TPI Crane Compucam, Ported heads TH400, Hooker headers and edelbrock mufflers (LOUD)no cats, 8" lift, 36" super swampers, 4.10 detroit lockers,

 

It's possible that your "custom chip" has a timing table that leaves it unchanged as you rev with no load-but not likely. If you rev from idle to at least 2400prm there should be noticable advance; which makes it look like a possible sensor problem. The GM code parameters are set so a sensor can be out of range without quite setting a code. I've had it happen with a MAF sensor- it eventually did set a code but not right away. If there is any way you can beg/borrow a scan tool; as stated above-the problem should jump out at you. Good luck-I know how this $@%$&^* can drive you crazy!



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86 406

 

Like Ed said, sometimes the answer is there in front of you. I had a similar problem not long ago. The car was progressively getting worse. One day while looking under the hood with the engine running I heard a ticking sound accompained by some engine shacking. Come to find out it was a bad spark plug. It was arching around the ceramic to the head. After changing them the car ran just fine.
BTW, I did not have any codes either.