Hi guys, I just bought an 88 camaro that was a v6 auto and was swapped with a 350 5.7 tpi out of an 87 vette, trans swapped to 5 speed manual out of an iroc all before i bought it. The guy told me i needed new plugs and wires and it wasnt idling well... IAC sensor was unplugged lol so once i fixed that it idles but rough. Now shes running smooth with new plugs and wires but when i was testing to see if she was firing right i pushed her a little bit and found out that sometimes when i give it too much throttle the rpms severely drop and i get a huge power loss. If i let off the throttle then reapply pressure it goes away. Also i can only really guess that the proper idle is by sound because the tach seems to read way higher than it should, but im guessing it because he didnt swap the tach from v6 to v8. Any ideas?

 

bump, i should probably say i always run 93 octane and i used a bottle of gum out the first fill up. When i pulled the old plugs, a couple of em were black, so maybe i need a fuel filter or take it to the shop and do a full clean on the injectors?

 

Can someone please help me out here?

 

My first thought would be that you have a dead spot in the TPS at WOT. Not uncommon for dead spots. The TPS is the same on all TBI and TPI cars from that era, V8 or V6. I would check it with an Analog ( not digital ) VM and place the meter in the ohm setting and watch the gauge as you open the throttle (not running) You want to see a good smooth sweep across the meter. If you hit a dead spot your needle will plunge suddendly then rebound back. Also the TPS could be lose or out of adjustment.

Second thought is that since this was a 6 banger and not a V8, the owner may not have switched out the fuel pump in the tank to a V8 pump. The V8 pump has more supply than the 6 did.

The fouled plugs could either indicate a leaking/sticking injector, oil blow-by due to valve seals or oil rings, Stuck open EGR valve ( which may be causing some of the idle issues too if it is not sealing completly) You should pull out the new plugs on those cyls that the old ones were black in and see if the new ones are also fowled. The old plugs may not have been the proper heat range which would also cause then to get black with carbon build up that is not burned off due to a too low of temp plug.

If the EGR valve is shot ( and most are after 20+ years ) it will cause a vacuum leak which will make the car run like ****. Idle air adjustment is critical for the computer to properly maintain idle. A sticking or shot IAC valve can cause a lot of headaches too.

TPI is a finicky motha' when things are not just right. As I have found out. But I like it.

And yes, the V6 tach will read higher ( about 33% ) than the correct V8 tach. You will have to do the resistor swap to fix it.

 

I had another thought too that the fuel filter might be plugged. I would think he would have swapped out the pump and the filter but I kinda bet he did not. I would bet this was a 2.8 MPFI car which would have had the correct PSI pump, but the pump volume is not enough to feed a V8. The filters might also have been different. The V8 might need a larger filter to promote more flow.

You would definitely see if it is a flow problem if you attach a gauge to the fuel rail and stick it out the hood so you can see it while driving. The psi should stay around 36-45 psi if the regulator is functioning properly. If it drops the below 30 or 20 at WOT accel, then that is your problem and it would be either FP, filter or regulator issue.

Personally, I disconnected the vacuum line to the regulator and run straight 46PSI to the rail. Since I have a larger cam and 1.6 rockers, it helps out the a/f ratio till I get the itch to try reprogramming the computer.

The computers ( speaking of which ) are almost all bad by now. If it was the stock orig computer that came out if the corvette, it may have some broken solder joints which would cause a loss of signal, grounding issues to the injectors and what ever else. That is an issue with all TPI MPFI and TBI cars of those years.

 

Hey man thanks for the advice, im changing the fuel filter tomorrow, ill keep you posted. Thanks again!

 

Hey x11nt4 thanks for the help again, i put a new fuel filter in yesterday. The old one was definitely smaller so once we put that in it breathes a little better but was still having the throttle problem. so we unplugged the throttle position sensor and it was doing wide open throttle fine, so im assuming thats the problem. Ill keep you posted. Thanks again!

 

Hey, glad to hear you are making some progress there.

I just remembered something I had read when I did a TPI swap, since this is an 87 I assume it is still a MAF sensor instead of MAP? If it is, I know a lot of ppl have problems with the MAF going bad. Although I don't recall if they had issue's at WOT, but usually a rough idle was due to the MAF. Supposedly you can tap on the MAF while running, and if it has a bad connection inside, it will run better. You might try pulling codes from the ECU and see what all is stored.

 

or ur computer may have a glitch or tuned wrong he could have possibly taken a 305 comp out of the iroc where he got the tranny so its not able to support the more air and different injectors