radiopat Posted July 22, 2003 Report Share Posted July 22, 2003 I've been having problems lately on my '88GP 2.8 with it hesitating when the engine is cold. What happens is when you give it a little gas either in drive or neutral, it will hesitate. The problem does clear up after about 10 minutes of driving. I just had a complete tune up done on it today, new plugs, wires, pvc, tb cleaned and had no improvement. Also, the egr appears to function normally. All codes are normal. Any clues to what it might be? Thanks. Pat. Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted July 22, 2003 Report Share Posted July 22, 2003 Please tell me that you've had the SPEED DENSITY UPDATE done on your car/engine!!?? Get rid of that EXTREMELY problematic MAF(Mass Air Flow) Sensor, it only causes problems. Besides that, I'm guessing that it's a fuel delivery problem. If it only happens when it's COLD, that means it's only happening when the engine is in what is called "OPEN LOOP". In "OPEN LOOP", the engine's computer completely ignores the O2 Sensor, and therefore cannot possibly compensate for a LEAN running engine until it has warmed-up and entered "CLOSED LOOP". So, you're probably running LEAN up until the engine is warm, at which point it will compensate, and increase the injector pulse width, therefore getting rid of your hesitation problem. That's all I can think of RIGHT NOW:) Quote Link to comment Share on other sites More sharing options...
radiopat Posted July 23, 2003 Author Report Share Posted July 23, 2003 I don't know if it ever had the update. I've only had the car a couple of months, but it does have the GM Mass Airflow Sensor. Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted July 23, 2003 Report Share Posted July 23, 2003 Look all around your engine compartment, if the update has been completed, the mechanic would have to place a sticker stating something such as "SPEED DENSITY UPDATE". With your engine idling, "BANG" on the MAF Sensor and see if the engine "stumbles", if it does, it's bad! That of course, is just ONE way to test the MAF... Quote Link to comment Share on other sites More sharing options...
Robby1870 Posted July 23, 2003 Report Share Posted July 23, 2003 If its not the MAF, then its nothing at all. I have had my car 3 years now, and it has always hated being cold. Even now in the summer, I have to let it come out of high idle (1000 rpms) before I put it in gear, then it has to get to atleast 130* before I can stop being easy on it. Thats the way it has always been. And, plus, IMO, you should be easy on any motor unit its at operating temp Robby Quote Link to comment Share on other sites More sharing options...
radiopat Posted July 23, 2003 Author Report Share Posted July 23, 2003 I just checked the engine compartment and it does have the speed density update sticker in it. Pat Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted July 23, 2003 Report Share Posted July 23, 2003 OK, that's good to hear... The ONLY other thing I can think of, and makes a lot of sense, is the ECT(Engine Coolant Temperature) Sensor. The reason you won't get a Trouble Code is because it's not EXTREMELY bad, yet. For example, it will only set a TOO HIGH code if it's reporting temperature above 270 degrees F for 20 seconds. It will only set a TOO LOW code if it's reporting a temperature below -37 degrees F for 1 second or more. So, as you can see, these two codes are pretty much COMPLETELY useless!! If you're ECT is stuck on 180 degrees F, for example, you would NEVER get a code, but you're ECM would ALWAYS think that you're engine was warmed-up when in reality, it was not at all!! I always rant about the uselessness of OBD-I trouble codes, and this is just ANOTHER example!! Here's a simple way to test your ECT, if you have a Digital MultiMeter. Measure the RESISTANCE of the sensor itself, the following is a table showing how OHM's translates to TEMP. 212 degrees F = 177 OHMs 158 degrees F = 332 OHMs 104 degrees F = 1459 OHMs 68 degrees F = 3520 OHMs 41 degrees F = 7280 OHMs 23 degrees F = 12300 OHMs -4 degrees F = 28680 OHMs -40 degrees F = 100700 OHMs My BET is that your ECT Sensor is "STUCK" at somewhere around 300-400 OHM's, or it's just not able to give readings that are above that... Check it out:) Quote Link to comment Share on other sites More sharing options...
radiopat Posted July 23, 2003 Author Report Share Posted July 23, 2003 I do have a digital voltmeter and I'll check it out. Before I bought the car I believe that had a new sensor was installed, however I have noticed that the temp gauge never goes beyond 125 on the highway but will go to 180 to 220 in the city, so perhaps thats where the problem is. Pat Quote Link to comment Share on other sites More sharing options...
Baddflash Posted July 23, 2003 Report Share Posted July 23, 2003 Your temps sound about right so I don't think your problem is there. My old 2.8 acted almost the same it would hesitate a little when cold and run fine after a couple minutes, mine did have the update to. It never really bothered me and I put over 350,000 Kms on that engine without any major problems. It just might be something you have to live with like Robby said. Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted July 23, 2003 Report Share Posted July 23, 2003 You DO realize that there is TWO Coolant Temp Sensors in your engine, right? The gauge sender is NOT the same Sensor that your ECM/Computer relies on for it's engine temperature input... Just letting you know... Also, just because people say "I think that's normal, that has always happened with mine"...doesn't mean it's OK, or something that you should live with...if the cars didn't do it when they were NEW, they shouldn't do it now... My 89 Cutlass with a 2.8L engine acts completely fine when it's COLD, most cars have a little MORE power when it's cold because it runs the A/F ratio slightly lower than the normal 14.7-1 Quote Link to comment Share on other sites More sharing options...
Baddflash Posted July 23, 2003 Report Share Posted July 23, 2003 Yes I am aware that there are two different temp sensors. :? I never said it was normal I said that it may be something that you have to live with. I don't know how bad his hesitates but mine was very, very minor and never bothered me enough to run around replacing sensors and crap trying to fix it. I think it really depends on how bad it is and if it really bothers you that much to spend a lot of money trying to track down a problem such as this. As he has replaced the basic stuff it now comes down considerably more expensive parts which isn't really obvious as to what they are. So again unless you have a lot of funds to spend troubleshooting it may be something that you he'll have to live with. Quote Link to comment Share on other sites More sharing options...
gmrulz4u Posted July 23, 2003 Report Share Posted July 23, 2003 Exactly...when someone says their car "hesitates", who the hell know's just HOW MUCH, besides the poster themselves... The word "hesitation" can mean a million different things, to a million different degrees, to everyone using this forum...it's not something as cut and dry as saying "my car won't start" etc... Also, an Engine Coolant Sensor costs close to nothing...spark wires cost A LOT more... Quote Link to comment Share on other sites More sharing options...
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