I am new here but I have 30+ years of auto repair experience. I have a 97 Camry with a fairly new rebuilt engine that literally over night developed a huge issue. I have searched for the last several months & no answers seem to fix it &/or none of the issues I've read match completely. At right around half throttle the engine sputters as if it's either spark knocking or has a shorting plug wire. It will die but as soon as it does you can put it in neutral & it'll immediately restart, as long as you stay away from that part of the throttle. It will never come out of it but if you baby it & feather the throttle a little it won't die & will eventually build up to highway speed.

There are NO codes at all! Oh and also I took it to a friend of mine that owns a transmission shop that has 40 years experience. He says it's a running issue not the transmission which it almost acts like.

Here's some history... About 15k miles ago the engine was fully rebuilt. New crank, pistons, rings etc plus a connecting rod. It had had a thrown rod. The head was gone through & obviously all new gaskets. The counterbalance was destroyed so not reused & the oil feed passage to it was plugged after reading several forum posts about this. it was broken in correctly & drove roughly 15k miles before this problem developed.

After this problem started we started simple with thinking it was bad gas. Checked the compression to make sure there were no internal issues. both compression check & leak down test were good. It progressed to replacing the fuel pump, regulator & fuel filter because we'd made a fitting to check fuel pressure & it was slightly low. Using logical reasoning brought us to that. When that didn't work we changed in order... the plugs & wires (tried 2 sets of wires) then went on to the coil packs, fuel injectors, coolant temp sensor & then its connector and then eventually changed the catalytic converter thinking it might be clogged. Seriously I can't think of anything else that could possibly make sense. TPS sensor has been checked as well & seems fine. I'm way past the point of throwing more parts at it lol

Also it has a new battery & alternator.

If anyone that reads this novel still has ANY ideas please let me know. I'm starting a new job that's 4 hours away & I'd like to be able to drive this car up there instead of leaving my SS up there.

 

Have you tried turning off the EGR system.

 

No. I have checked the EGR valve. It moves perfectly with a vacuum pump attached & stays as long as there's vacuum. I've replaced the switch that controls vacuum to it & triple checked the routing of the hoses via a vacuum schematic. One thing really odd... the cap on the vacuum modulator that feeds the EGR has popped off twice. It now has no cap at all. So you think bypassing the entire EGR might make it run better?

 

Bypassing to turn it off (valve closed). The engine can have issues if the valve is too far open. Engine will run OK with valve closed.

Can you sneak up on the throttle to avoid the miss?

Do you have a real time ODBII scanner to monitor the engine before and after the miss starts for parameter changes?

 

Nope once in the range of throttle that causes the issue, any farther on the throttle just makes it die. Yes I've hooked up my OBD II scanner for live info but honestly I can't see what the issue is on it. What trips me up is everything we've replaced & no results yet there have never been any codes. I will try to eliminate the EGR entirely this weekend to see if that helps & report back. Thanks for the ideas.

 

Read info at link below:

Fuel trim can be a valuable diagnostic tool - Eastern Manufacturing

 

I still haven't had a chance to put the code scanner on it for live feed. But I did block off the EGR completely & it made a BIG difference. It still stumbles a little at half throttle but it no longer dies & you can throttle out of it. So we're working closer to the issue

I'm sorry for slow replies but I've got a lot going on right now. And I really do appreciate the help.

 

No need to apologize and appear on the right track.

Vacuum to the EGR system is either on/off. This is accomplished via the VSV valve. This valve turns engine vacuum to the system on/off based on a engine computer signal (applies 12V to turn on).

Once the system is on. An EGR modulator (diaphragm valve) senses varying engine intake vacuum to vary vacuum to the actual EGR valve.

The EGR valve may have an electrical position sensor to determine where the valve is and provide this info to the computer.

It could be a bad modulator or perhaps position sensor.

Also suggest checking out the EGR valve for sticking, excess carbon, etc.

 

It's fixed! And now I feel really really foolish lmao. I drove it again the other day with the EGR unhooked. Did the same it had been doing before. Died. Then I had my son in law come over to drive it just to get a second set of eyes on it. He was baffled as well. We discussed it & decided the best plan of attack was to pull the timing cover to check the timing belt, crank sensor etc. Basically start from the beginning & give it a once over. So the next day I went out there & it just plain wouldn't start. So I went to check the crank sensor... the damn connector wasn't plugged in all the way. I pushed it in & made it click. I decided I better test drive before I take anything apart. Low and behold the damn car is 100% fixed. In fact I can't believe how well it runs. I guess because all those new parts I threw at it trying to fix it basically made it a new car haha.

Well now my old beater is drivable and I can put my SS up for the winter in the garage!

 

Greet job!

Thanks for posting back with the find.