After some engine upgrades, cam, heads, LT and TQ converter. The car has never run right even after many tweeks of it's tuning. The tuner is a professional and has been featured in several automotive magazines. Yet, the car won't idle correctly what's the problem?

When coming to a quick deceleration the engine would stumble and stutter. The RPM's would swing up and down trying to find an idle speed, to the point the car would be on the verge of dying. It was even worse when the A/C was turned on. Also if you drove it a long distance and then came to a creeping roll in heavy traffic, the engine would go into that nearly dying. I'd have to shift it into neutral to keep the engine from dying. It also experiences a strange slippage at about 40-50 mph, as if the car doesn't know when to lock up the torque converter.

Any suggestions? Help please...

 

Vhttps://www.youtube.com/watch?v=o_2gtlGy_UU

 

I haven't a clue about this tuning business. I figured the professional would know what he's doing. He comes highly regarded, people bring their cars from states far away to get theirs worked on exclusively by him. However, so far ever since the upgrades the car runs horrible when having to come to a quick stop or creeping along like in a parade.

 

Sorry man, the vid does explain some of the problem with idle with a big cam, it's informative at best.

 

Sounds like the tuner either didn't have time or didn't care enough to bother adjusting the idle tables. It's very important to accurately model the airflow of the motor, especially with a big cammed car.

 

Yea it just needs fine tuning in the idle areas. Tuner needs to take another look at it.

I always strive to tune a car the best i can. I would never let a car go out the door with it running like tht.

 

It's not that big a cam, 224/232 recommended by the tuner. I laid out clear instructions that I wanted it streetable and well mannered, not a loping, surging power house. These new cars and their pc programming is way over my head. The Tuner is highly reputable and considered one of the best in the country, but my car doesn't idle worth a crap. I fear it's going to die in traffic, and has done so a couple of times. There is no joy in driving it, and it feels more like a battle of dread to take it anywhere.

The Mods I had done that he recommended and installed:
Livernoris Stage 3 heads
Crane Cam 1449121
FTI 2800 stall TQ converter
ARH Longtubes
Walbro 255 lph

He also dyno tuned the vehicle. I've taken it back to him several times because it don't run right in street driving. Scared to turn on the A/C car might stall. Scared to have to stop quickly or the car will stall. If just creeping along in traffic even with no A/C on the car will nearly stall, I have to shift it in neutral to keep it running.

 

You have the ability to post the tune and a log?

 

Not bashing anyone but just because they are in magazines or even tune fast cars dont have anything to do with driveability tuning. I know some of the best race car tuners in the NHRA but they couldnt tune a stock computer car with hp tuners tomorrow. WIth time they obviously could figure it out but making a car fast and making one drive good on the street are different. From your mods listed and what your describing it seems like the tune but without seeing the tune and some data logs everyone is just guessing.

 

Sounds like a vacuum leak to me. Dont blame the tuner just yet

 

Amen. That cam with -2* of overlap and an auto should drive just fine if the tuner knows what theyre doing. Only other thing would be to check for a vacuum leak.

 

A vacuum leak is a possibility but I find it highly unlikely. When he tweaked it to do better with the A/C on things really got weird. It was for a time running decently so long as the AC was off. I'm not sure how upping the RPM's for when the AC is on would effect or change the tune from when it was off?

I suppose I'll have to take it back to him, but I don't know how to explain what's happening and why can't he get this tuned right?

 

I've literally fixed that issue with the AC by updating a single table. The tuner just needs to spend some time with the car. Make a list of all the issues and talk to him about it.

 

 

That's all greek to me, see why I have no business with an HP tuner. I'd really screw things up!

 

Go back to the tuner.

A/C puts a load on the engine. You have to tune for it.

 

If his tuner cannot diagnose a simple vacuum leak he is a useless hack. The tuner is absolutely to blame for the current situation. He recommended a cam, then "tuned" the car. I have seen multiple examples of "magazine star" tuners and shops who do absolute crap work. The best reputations are sometimes built on the backs of unsuspecting customers who don't know any better.

 

have you considered it may be a mechanical issue as well? like mentioned above regarding possible vac leak. could be something else that may had been installed improperly during the cam swap?

 

The greatest minds that ever lived still made far more mistakes than solutions. Thats why the greatest minds dont believe in mistakes, rather see the errors as lessons. I'm trying to help the OP sort out his car, not sling mud on a tuner. It sounds like a vacuum leak and they are easy to find and repair. If the OP sprays quick start around all his vac posts and sensors while idling the engine and the RPM doesnt change then its likely not a vac leak and we can look at other potentials. Its a process of elimination no matter how good/bad the mech and tuner are.

If its drive by cable and automatic with a cam these are notoriously difficult to dial in the IAC stepper. I suggest drilling a larger hole in the throttle body for starters if this is the case AFTER its confirmed there is no vac leak.

 

Drilling a hole in the throttle body is exactly the type of stuff gametech is talking about....hack moves. There is absolutely NO reason to do that unless it has the biggest if the big cams. That's old school tech for people who don't know how to setup and tune a car properly.