Hesitation at throttle tip-in...help please.

[dgreen1069]

Here's the deal. My car is bone stock with 5800 miles on it. I have had the car for about a year and have put about a 1000 miles on it. The engine starts right up and idles, but the idle has always seems just a little rough. There is a hesitation at throttle tip-in.....regardless of speed. At any throttle position past tip-in things seem to be fine.

I have replaced the plugs, cleaned the intake, used BG44k to clean the injectors, and tried new plug wires....the problem continues. The original owner had an aftermarket chip in the car which I promptly removed and replaced with the factory chip. The hesitation and idle did not change from one chip to the other. I had the IAC and BLM's checked and they were in tolerance.

I just had my A/C recharged and I asked the Buick dealership to try and fix the problem. Those boobs came back and recommended everything I had already had done. They then told me the car might have some contamination in the injectors which is causing the problem. My problem with that idea is that the injectors work fine above anything more than tip-in....to me that rules them out. Those jerks charged me $92 for diagnostics and the car runs exactly the same. They said they bumped up the idle and adjusted the MAF, but I think they made things slightly worse. I don't mind spending money fixing things, but throwing it away for nothing infuriates me. Please help. I need the most likely causes of my problem. There have got to be others who have had the same problem in the last 18 years.

 

[Steve V]

Causes..

You can not adjust idle or MAF on these cars it is in the chip. Get the stock chip outta there it's old tech and not good on todays gas. Get a Turbotweak chip,takes about 2 weeks it'll be the best $75 you spent on the GN. Your car only has 5800 miles I am jealous. The dealer is most likely only gonna F---up your car fine another TR mechanic in your area. Nothing against Red,but there ARE a lot better chips out there, www.turbotweak.com..Eric Marshall is the best. Good luck.

 

[soundguy]

you are experiencing exactly what mine did. It would hestitate just as you began to touch the gas but fine after. I found it was the TPS was set way too low. .25 on mine, so basically the computer thought the car went into idle as you pressed the gas a bit and the TPS read .4 .

 

[TurboDave]

Here's the deal. My car is bone stock with 5800 miles on it. I have had the car for about a year and have put about a 1000 miles on it. The engine starts right up and idles, but the idle has always seems just a little rough. There is a hesitation at throttle tip-in.....regardless of speed. At any throttle position past tip-in things seem to be fine.

I have replaced the plugs, cleaned the intake, used BG44k to clean the injectors, and tried new plug wires....the problem continues. The original owner had an aftermarket chip in the car which I promptly removed and replaced with the factory chip. The hesitation and idle did not change from one chip to the other. I had the IAC and BLM's checked and they were in tolerance.

I just had my A/C recharged and I asked the Buick dealership to try and fix the problem. Those boobs came back and recommended everything I had already had done. They then told me the car might have some contamination in the injectors which is causing the problem. My problem with that idea is that the injectors work fine above anything more than tip-in....to me that rules them out. Those jerks charged me $92 for diagnostics and the car runs exactly the same. They said they bumped up the idle and adjusted the MAF, but I think they made things slightly worse. I don't mind spending money fixing things, but throwing it away for nothing infuriates me. Please help. I need the most likely causes of my problem. There have got to be others who have had the same problem in the last 18 years.

Never take your car to a dealership, or any non T/R specific mechanic for that matter. They'll just do exactly what they did to you. Rip you off.
As was stated, the MAF and idle speed are non adjustable on these cars, soooooo what they've done is to mess with the minimum air bleed screw and messed up your IAC and TPS at the same time. These two adjustements being out of spec (as they are on your car now) will yeild exactly the symptoms you're suffering from.
You need to find someone near you that actually knows what they're doing around these cars to get the IAC(minimum air bleed screw) and TPS properly set, once that's done your problem will be cleared up.

 

[Fuelie600]

Where are you located?

 

[dgreen1069]

Nothern VA...just outside Manassas. Thank you all for your responses. My gut feeling the whole time has been that my problem was tune related. They did exactly what you guys said....messed with the minimum air mixture and the TPS. It's hard to tell, but I think it is worse than it was before. It's driving me insane!!!!!!

 

[dgreen1069]

Is it possible to play with the TPS without the use of a scanner? Would I be able to make small changes to fix the problem or am I likely to make matters worse?

 

[TurboDave]

Is it possible to play with the TPS without the use of a scanner? Would I be able to make small changes to fix the problem or am I likely to make matters worse?

IMHO, absolutely not. There must be a way to monitor TPS voltage (can be done with a voltmeter) if you're going to adjust it.

There does exist a procedure somewhere on resetting the IAC, but again, IMHO, it's useless in most cases and especially if the air bleed screw (which is usually mistaken for an idle speed screw) has been fiddled with. You've got to have a scan tool hooked up to monitor IAC values to get it right.

 

[acoen]

Here is the Service Manual IAC reset procedure. You will not need a scan tool, but you will need a digital volt meter for adjusting the TPS and a good portable Tach...Timing light with a Tach feature should work just fine. Tuning these things without a good scan tool is a little tough.

IAC Reset Procedure
Service Manual
Procedure
1. Ground ALDL diagnostic lead (short the top two rightmost pins in the ALDL
connector).
2. Turn on the ignition (but don't start the car).
3. Wait 30 seconds.
4. Leave ignition on and disconnect the IAC connector.
5. Remove the grounding from the ALDL connector.
6. Start the car. The car will probably run rough and may stall. Just
restart and try again.
7. Adjust the throttle stop screw to set the idle to 500 RPM +/- 50 RPM.
8. Turn the car off and reconnect the IAC connector.
9. Turn ignition on and adjust TPS to proper settings. (.42-.44 at idle is
typical)
10. Repeat procedure until the 500 RPM +/- 50 RPM in step 7 can be
maintained while TPS is at proper idle setting.

HTH,

Aaron

 

[Razor]

Get a scanmasterII for the car. The money spent at the dealer and all the other parts thrown at would of paid for it and then some. Especially the grief thats ensued not having a simple diagnostic tool.

While IAC can be set up as described above, i've never had predictable results doing so.

Your issues are TPS and min air rate(IAC) adjustment.

Lastly, one thing not mentioned was throttle body cleaning.

HTH

 

[Just a Six??]

As Stated Get a Scanmaster!!! BEST $200 you will EVER Spend on the car aside from a new chip by Eric custom burned for your car!

 

[dgreen1069]

The intake was cleaned using GM's intake cleaner. To be honest, it was clean before I started. Is the Scanmaster hardwired into the car or does it just plug into the test port? Is there a source for used ones? Anyone familiar with Reds Hot Air's shop in Newport News, VA? I sent him an email and am waiting for a response. Thanks for all the advise. Dave

 

[TurboDave]

Here is the Service Manual IAC reset procedure. You will not need a scan tool, but you will need a digital volt meter for adjusting the TPS and a good portable Tach...Timing light with a Tach feature should work just fine. Tuning these things without a good scan tool is a little tough.

IAC Reset Procedure
Service Manual
Procedure
1. Ground ALDL diagnostic lead (short the top two rightmost pins in the ALDL
connector).
2. Turn on the ignition (but don't start the car).
3. Wait 30 seconds.
4. Leave ignition on and disconnect the IAC connector.
5. Remove the grounding from the ALDL connector.
6. Start the car. The car will probably run rough and may stall. Just
restart and try again.
7. Adjust the throttle stop screw to set the idle to 500 RPM +/- 50 RPM.
8. Turn the car off and reconnect the IAC connector.
9. Turn ignition on and adjust TPS to proper settings. (.42-.44 at idle is
typical)
10. Repeat procedure until the 500 RPM +/- 50 RPM in step 7 can be
maintained while TPS is at proper idle setting.

HTH,

Aaron

This procedure is all well and good if you're back in the mid 80's with no scan tools (this was a dealership procedure back when scan tools were extremely rare)(these cars were ahead of their time afterall).
Problem is, it only works (properly) half the time and is a crap shoot at best. And certainly isn't the procedure to use when some fat fingered mechanic has fused with the air bleed adjustment (such as this case).
With the availability of scan tools (especially easy one's like Scanmaster) I can't for the life of me imagine why anybody would still be using or extoling this procedure.

Oh well...

My recomendation. do it right the first time (scan tool), get the numbers where they belong with a scan tool (You don't have a clue what the IAC numbers end up with the above procedure), so you can't possibly say things are for sure, right.

 

[Steve V]

Red is a good guy,he is also a very busy one. Builds high HP buicks.