00 3800 - Hesitates between 15-2000rpm when driving?

Hello,

I have a 00 Regal with the 3800 SC motor in it. About 6 months ago it would sometimes (not all) hesitate around 1700 rpm or so on the highway driving. It felt like an iginition problem so I had the following checked and or replaced.
-new wires
-new plugs
-new coil packs
-fuel filter replaced
-fuel pressure checked

After having this done..it seemed ok for a month or so. Then the problem began reoccuring and now will do it almost every time again. If I nail it when it starts this and get to higher rpms..its fine..and its only at this RPM range when driving that it hesitates (can't replicate in park).

I don't know what else to try? I thought possibly the Ignition Control Module..but since its a $160 part I thought I'd check for oppinions first before I just replaced it.

Its frustrating because it doesn't trip any codes..but its there with a miss (I took it to a local garage and they didn't have any more ideas than I did).

Thanks for any help.

although i highly doubt it, if you have a ohmmeter/voltmeter/multimeter test the TPS for flat spots, but the few TPSs i know are well built and rarely go bad after 15 years.

i'll check TSBs tomarrow if i get a chance.

although i highly doubt it, if you have a ohmmeter/voltmeter/multimeter test the TPS for flat spots, but the few TPSs i know are well built and rarely go bad after 15 years.

i'll check TSBs tomarrow if i get a chance.

I do have a meter. Sorry but didn't get the acronym..what are you referring to by TPS?

Thanks.

no TSBs found

TPS-throttle position sensor, mounted on the throttle body, attached to the shaft connected to the throttle plate. 3-wires.

with the key off/out. if you disconnect the harness, and attach your ohmmeter leads to the middle and ether side terminal of the sensor. move the throttle by hand. the resistance should change, slowly move the throttle all the way forward and back, and also focusing on where the throttle is at around 1500-2000 RPMs as you said, watch the resistance carefully any non-linear reading inducates a flat spot on the TPS's internal resistor.

again this is just a shot in the dark idea. but when the TPS gets a flat spot, the computer will not get the porper reading, and can not calulate the engine load accuritly.

Thanks A lot....I will try that this weekend. It seems to be getting worse with time..I need to figure it out (these types of problems are always annoying..when its hard to diagnose)

any luck?

This may or may not be your problem, but I had a similar problem between 2000 and 2500 RPM. Couldn't figure it out and it was just annoying, driving at 70 MPH and feeling like the engine was cutting out. Went through all the engine stuff and could never find a problem. Decided to live with it. Well, I got on a transmission kick with all my cars and welded drain plugs onto all the tx pans so I could regularly drain the tx fluid (every 5000 miles) between filter changes (25000 miles). Since I hate taking my car in anywhere, I figured this not only keeps my cars out of the hands of others, but it also keeps my tranny cleaner than just changing it every two years or even every year, and it costs about the same as having the tranny flushed at a shop. Anyway, the problem seems to have disappeared after the second drainage and replenishment of tx fluid. Go figure. It may be worth a try, especially if you plan on keeping the car for a while.

Hi.
Could you describe the hesitation in more detail?
Perhaps the torque converter lockup is not staying engaged, that could feel like a miss as it cuts in/out.

An OBDII scantool may show what is causing the problem.
Check if the stored long term fuel trim value is rich or lean.
It can also read the torque converter lockup signals and you need to verify that the O2 sensors are working.

You can check torque converter lockup manually by observing the shift points and engine RPM. To verify that it is in lockup mode drive steady in high gear such as 60mph and then tap (and release) the brake pedal. That should release the lockup momentarily and if it was properly engaged you will see the engine RPM rise slightly for 1 second right after you tapped the brake. Then it should go back into lockup on it's own.

Other possibilities:
Contaminated fuel, gets worse over time....hmmm......
Wrong spark plug wires - new ones are not always the right resistance for your vehicle. Aim for ~ 7000 ohms. Some brands are 2x too high.
Oxygen sensor slow to respond, contaminated or wiring problem.
Fuel injector problem (clogged or leaking).
Leaking fuel pressure regulator (check for fuel in the vacuum hose).
Those new spark plugs didn't get fouled did they?
MAF Sensor and wiring. MAF: mass air flow.
EGR valve issue. (Exhaust gas recirculation)
PCV valve problem. (positive crankcase ventilation)
Transaxle range switch problem or maladjustment. Does it still miss at 1700rpm if you manually keep it in 3rd gear?
Did they check the fuel pressure under load?
Faulty crankshaft position or camshaft position sensor.
Intermittent ignition feed circuit or sensor ground to the crankshaft or camshaft position sensor.
Loose motor mounts.
Restricted exhaust system.

Good luck.

I am a GM man all the way but they do have there little quirks here and there. I once talked to a Toyota Lover and he asked me why I drove GM products. I told him I knew how to work on them. He then replied if I would drive Toyotas like him I wouldn't have to know how to work on them because they don't break down. I think he is full of it but anyway on to your question. I do have some significant experience with this problem. GM did have some problems with there lock up converters but from my experience it is more likely a much easier solution. I had a 96 regal GS with a 3800. At around 190000 miles it decided to break a valve lock and drop a valve half way into the cylender but not completely. What this did in turn was cause the piston to smack the valve a thousand times before I got her shut down. Thank god it happened at idle in traffic. To make a long story short that cylender fouled a plug obviously. I took the head off and replaced the valve, put the engine back together and drove the car. I didn't think to check that plug before I put it back in the motor. The car ran perfectly but it did develop a miss wien i was at cruising speed and it would cause the rpm's to flutter up and down and what was ultimately happening was that cylender would misfire and cause the lock up converter to disengage and this would happen over and over but it wouldn't happen consistantly. I then went thru the drill fo checking coil packs. I had three individual ones. You can check these with a basic multimeter. They all were perfect. Then I checked plug wires with a multimeter. This is easy also. The I checked the plugs and sure enough that cylender had a dirty plug from the valve problem I had before. I cleanded the plug and reinstalled it. I never had another problem after that. Drove the old girl another 20000 and sold her. I just saw it the other day cruising down the road. These cars are great and good luck with yours.

if it worked for a month or so, i'd check out the plugs and wires in the dark ( for arcing).. if you are using third party brands, they don't hold up as well as delco parts..

I had a similar problem '94 Regal GS with 240,000.
There was a knock in the engine and the knock sensor was retarding the spark. I had a mechanic freind move the knock sensor off the block and eliminated the problem.