gun4hire

Hey guys!

I did try to search through old posts and didn't see anything similar to what I am experiencing. I hope you can help me out here. I have a problem that my car will not rev past about 2200-2500 RPM.

A mechanic friend of mine and I have checked the spark that comes thru the wires with a snap-on tool - it's reading very low "kb's" according to him.

Thinking it ignition related and was possibly related to the distributor, I swapped it out... no change. Cap/rotor are new. Thinking it was plugs, we swapped them out - no change. Thinking it was the coil I swapped that out - no change.

With a scan tool connected, the O2 sensor is a bit 'lazy' but it is doing it's job. At idle, the car runs fine and bounces between rich/lean. TPS volts look good. Brand new map sensor since I broke mine reassembling the intake.

It starts fine (actually VERY easy) Only when I bring the RPM up it wil go rich and around 2200 is bogs down. Car does die, just won't ramp up any faster RPM. It's blowing grey smoke (not black and not white).

The car has new accel 8mm wires. I used to have a LT4 hot cam and TFS 23* heads but the car never ran quite right...so I've put it back stock save for an ait pump delete and hedman hedders. The EGR is in place, but disconnected. I checked this to make sure it was sealing properly - it was.

Two things I have yet to check are the vacuum and the compression ratio. Car has over 100k on stock engine. My friend indicated that low CR can cause low KB's on the wires since there is more resistance in the plug 'arc' in the cylinder (presumably from a poor air/fuel compression = less volitile mixture). I could also have a vacuum leak somewhere - but why would it kick in only at higher RPM?

Of course, I suppose the new plug wires could be crappy too...

Any other suggestions? I feel like I just keep throwing money at the problem... I'd like some pointers - maybe someone on here has had the problem before.


Thanks in advance...

Richard

Sitting Bull

The catalytic converter might be plugged.

IROCThe5.7L

^ What he said.

gun4hire

Didn't think of that...but wouldn't that affect it at idle too? How about the KV's on the wires? It is something to check though, thanks!

Scrote

A pluged exhaust may not cause a problem at idle because the engine does not have to expell as much exhaust from the cylenders as it does at high RPMs. My guess would be a plugged cat or other exhaust component. As far as the low voltage in the secondary ignition....it could be a lot of things. If the primary coil is fine, the dist is new and your high tension leads are in good shape you should have good voltage.

Disconnect the cat from the Y pipe and try to rev it on open manfiolds, if it revs up, you found the problem.

Good luck,
Erik

gun4hire

OK, I just bounced this off my mechanic. He didn't seem to think this would be the case - in his experience the car would still run even at high revs - it just wouldn't have any power...

Since it's easy to drop the Y off the hedders, I'll still check it..just wanted to relay that info. The other thing is that if it had a clogged cat, wouldn't it be muffled better? Its pretty darn loud and seems to push plenty of air out the exhaust.



Why is the tem 'high tention leads' not ringing a bell? How can I check this?

Is it possible for new accel plug wires to have too much resistance? I'm gonna try swapping the old wires back on since I still have them to rule this out.

Quote:

Disconnect the cat from the Y pipe and try to rev it on open manfiolds, if it revs up, you found the problem.

Neighbors are going to LOVE me!

IROCThe5.7L

If your cat is plugged bad enough, you will not be able to rev it high. How would it be able to high rev if it couldnt get rid of the exhaust fast enough if it was clogged?

gun4hire

True, but would it just happen all by itself? Car has been run off/on but mostly sitting over the past 6 mos. What also makes me wonder is that it is still rich and I get plenty of rich exhaust...not like it's just barely puffing or whatever...

I'll still check the cats, but I dunno....

Rally Sport

is there any way to check the cat without taking the exhaust apart? I'm having the same problem where the car bogs at 2200-2500 rpm's, but mine only does this occasionally.

Chris Ja

Rally Sport yours sound like a fuel pump starting to go bad.
I have seen alot of bad cat converters over the years. They will bogg the engine down to the point of stalling under load. They will idle fine. They will run very rich. If you had a injector bleeding down and the car sat for 6 months that would do it. It would cause alot of back pressure in the engine and load the engine up. In turn that would coat the plugs. Pull a plug and see it it is wet.

gun4hire

In my case, the plugs are fouling - but not to the point of being wet. I will add that when I had the LT4 HOT, LT1 intake and TFS 23* heads that the plugs would be wet when I was troubleshooting. One of the reasons I got fed up with that and am going back stock.

Thanks for the added info!

Rally Sport

I hope this isn't a fuel pump problem because I just replaced it this fall and it cost a lot of $$$$
So if I pull the plugs and it isn't wet, what do you think it is?
I just put in a Jet Stage 2 chip and now problems are happening, but they don't happen all the time. With the chip in, my cars performance has been way better, but then occasionally she tries to die. Im afraid if I put the stock chip back in im going to get crappy performance again.

stevem

you could pull out the O2 sensor if you do not want to drop the exhaust.
but dropping the exhaust is the best idea.
HAVE YOU CHECKED YOU AIR FILTER(S)?????????????????

gun4hire

Since I have speed density (no MAF) this happens even with the throttle breathing open air.

O2 sensor is as bad as dropping the exhaust IMO...

I'll updateyou guys once I have tried this..

LT1Powered85Z

****** means "Spark Plug Wires"...he's a mechanic, he uses technical terms.

Eric