Issue starting and stall at high rpm

[devin1992]

My 1992 Sho has been having an issue starting randomly recently, it will crank but wont turn over, but 1 hr later will start up perfectly, it will start if i give it gas while turning the key usually. I know it isnt the starter, battery or alternator they are all brand new. Just before the starting issue came up i was coming off a stop sign onto a straight road and the car didnt respond to throttle imput after i shifted into second gear from first at probably 35-40mph. It behaved like neutral no acceleration. After i pulled over the car was fine and behaved normally this happened again when i did another 1st gear pull a few days later when shifting to 2nd so i think it has something to do with high rpm, ive been driving slow and the car has been fine as long as i dont launch it haha aside from the starting issue. Any advice would be appreciated im new to cars and am not sure where to look or how to troubleshoot from here. Sometimes my rpm and temp gauge display incorrectly not sure if related to the other issue, and for a few months ive had an exhaust leak but this didnt seem to cause an issue, did many pulls in the car with no problems until the current issue.

 

[devin1992]

Forgot to mention the starting problem began almost immediatly after the car "stalled" when shifting at high rpm

 

[zoomlater]

Pull your codes and report back, you should have three digit codes for a 1992 car

SHO Phoenix Project

 

[devin1992]

Pull your codes and report back, you should have three digit codes for a 1992 car

SHO Phoenix Project

Will do, no check engine light or anything on the dash ill do this when i get off work thank you.

 

[Dale Leonard]

Your cats have stopped up internally and are hindering your high speed and causing high backpressure.

 

[BaySHO Performance]

I second pulling codes. Very few of them cause the CEL to come on. You will find lots of useful info here as well as code checks:

EEC Self Test Procedure - V6SHO

Sometimes it's difficult to start these cars when hot because of fuel vapor lock. Giving it some gas while starting usually does the trick.

Unlikely you have a blown catalytic converter unless the car has misfired badly. A typical symptom is significant loss of power across the rpm range because a piece of blown cat has got stuck in the cat back and is creating huge back pressure.

If no codes, clean the MAF elements with an electric cleaner such as:

https://www.autozone.com/miscellaneous-cleaners-and-degreasers/electrical-parts-cleaner/p/crc-lectra-clean-3000-electrical-equipment-cleaner-19oz/943144_0_0?searchText=lectra

I've had lots of cases where the car will accelerate fine under gentle acceleration, but bogs down when given gas because the dirty MAF is throwing off the air / fuel ratio.

The tachometer misbehaving points to a bad camshaft sensor. If so, you will have a code for it.

 

[Dale Leonard]

My cats came apart in my 1989 SHO and never gave a code or anything else. But it would bog down on high RPM and would idle and run normal until I got on it. Never rule out the stupidest thing as it may bite you in the butt. Took me quite a while to figure it out. Finally bit the bullet and removed the cats. When I stood them up on end to try to visually inspect, pieces fell out from the engine side of the exhaust pipes. I cut a window in the top side of each cat and removed all interior parts and welded up and reinstalled. Ran way better and never threw a code. Did not regret it. Have owned 5 more over the years and cleaning out the cats was the first thing that I did after getting the cars home. I also have 3 SHO's sitting in different state's of repair. Best cars I have ever owned.

 

[loganbro28]

Had similar symptoms with a nissan MAF sensor maybe clean the MAF or get a new one.


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[BaySHO Performance]

My cats. When I stood them up on end to try to visually inspect, pieces fell out from the engine side of the exhaust pipes.

Ouch. When a cat lets go on the engine side pieces can get sucked back into the engine, scoring the cylinder walls beyond repair. Looks like you lucked out, but for jollies you might want to stick a bore scope into the cylinders. The vertical scratch marks would be plainly visible, unlike the factory cross hatch will be very faint and at an angle.