Car hesitates while driving, idles high while sitting

Tiny
FORMULAONEMAN
  • 1994 BUICK CENTURY
  • 100,000 MILES

Buick Century 2.2 EFI with OBD 1.5. Car hesitates at speed (kind of bucks), and it sometimes idles high when sitting. I've replaced the plugs, wires, air filter, fuel filter, fuel pump, and throttle position sensor. The hesitation doesn't happen all the time, but does happen quite a bit.

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Wednesday, September 19th, 2012 AT 5:21 PM

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Tiny
HMAC300
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Scan for codes and check fuel pressure it should be 41-47 if pfi or 9-11 if tbi. Check gasket under tbi for leaks, spray with choke cleaner if rpm changes you found the leak. The hesitation at speedmay be the torque converter clutch kicking in and out, depends on what speed it is

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Wednesday, September 19th, 2012 AT 7:51 PM
Tiny
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OK thanks I'll check the items you listed. However, I did spray around the manifold, and didn't get any idle changes. Also, the TC clutch is disconnected because it was making the engine stall at stop signs, and I haven't had a chance to change it. The hesitation is at speed (anywhare between 30 and 65 mph or so).

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Wednesday, September 19th, 2012 AT 8:05 PM
Tiny
SATURNTECH9
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Have you checked it for a sticking/bad egr valve?

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Thursday, September 20th, 2012 AT 6:02 AM
Tiny
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No I haven't done that yet. What's the procedure to test it, or should I just go ahead and replace it and the solenoid? Last night driving home (around a 20 mile commute), it was doing its hesitation thing, then the check engine light came on, and the hesitation stopped. Problem with the check engine light, is that my code reader won't read an OBD 1.5, and the Buick dealer wants $60 each time. The OBD 1.5 is kind of an odd ball one, and you can t jumper it either. Does anyone know a way to get the codes out? This is a "commuter" car that I bought back after I hit a deer with my good car last year, and I don t want to spend a bunch of money fixing it.

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Thursday, September 20th, 2012 AT 12:34 PM
Tiny
HMAC300
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Cross a&B on the aldl with a paper clip. Count the light flashes like 12 24 etc. Come back to the site and look unedr trouble codes obdI. It may also be the egr contol piece whichi is electric

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Thursday, September 20th, 2012 AT 1:40 PM
Tiny
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This is an OBD 1.5, not OBD 1, you can t jump it. It's kind of a high breed between 1 and 2. It has an OBD 1 block, but no B terminal wire. The GM OBD reader will read it (at $60 a shot), but an OBD 2 reader won't. I think it s an interim step between 1 and 2 that GM did before they went to 2 in 1996(?).

By the way, thank all of you for your prompt and helpful replies! I m going to donate as soon as I figure this out.

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Thursday, September 20th, 2012 AT 1:54 PM
Tiny
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Oh that's t right they only used that on olds and buick it has the 14 hole aldl. They went to obdII in 95

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Thursday, September 20th, 2012 AT 1:56 PM
Tiny
SATURNTECH9
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Its a 16 pin connector like the obd2 and gm went to obd2 in 1996 like everyone else because it was federal law. That is a pain when there obd1.5 to find a cheap scan tool to read them you could get a old tech 1 scan tool or a pro link scan tool on ebay. Let me see what I can find for you.

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Thursday, September 20th, 2012 AT 3:23 PM
Tiny
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If you want to read the codes and read live data etc to figure this out
your going to have to get a more advanced one like a mac tools task master thats the one I have or a matco pro scan plus or otc nemisys cornwell tech plus.I bought mine used on craigs list you can look on ebay sometimes on ebay ones with the older software you can het ffor 200 or under.

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Friday, September 21st, 2012 AT 3:34 AM
Tiny
SATURNTECH9
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Looks like the actron cp9185 and cp9190 will read that car also. But the other scan tools I mentioned are way better.

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Friday, September 21st, 2012 AT 6:54 AM
Tiny
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I have a CP9190, and I can't get it to read the codes. Seeing as the hesitation/surging stopped when the check engine light went on, doesn't that point more towards the EGR solenoid?

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Friday, September 21st, 2012 AT 12:40 PM
Tiny
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Not necessarily. All it means when it the light went on is that it went into open loop so it automatically richens themix and the sensor don't work the computer anymore.

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Friday, September 21st, 2012 AT 1:32 PM
Tiny
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We don't even know what codes it has so that is total spectulation.I was reading reviews on amazon on the cp9190 and one of the reviewers was saying that it read obd1.5 I guess there wrong.I have a cp9190 but have never tried it on a obd1.5 one car.I know my mac taskmaster lists your car on the software with 2003 software up to 2010 software updates. The other scan tools I mentioned use the same software the non. Actron scan tools.

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Friday, September 21st, 2012 AT 8:26 PM
Tiny
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I'll try it again this weekend. Maybe I did something wrong (wouldn't be the first time). Someone just told me that O'Reilly auto parts might have one that works for free rental.

Again, thanks for all the help!

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Friday, September 21st, 2012 AT 8:41 PM
Tiny
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Give the rental a try that wouldnt be a bad try.

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Saturday, September 22nd, 2012 AT 1:17 AM
Tiny
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As it turns out, my CP9190 does work. The lighter outlet in the ash tray doesn t work, and I didn t catch it. The analyzer needs 12v power to run the diagnostics. All it said was connect ADL. When I connected it to the battery, it worked fine.

So, it s getting a code 22 TPS voltage low. That s the only code. I reset it, and the check engine light came on while I was driving to work this morning. I ll check it again tonight when I get home. I changed the TPS back a couple of months ago (my $60 dealer charge that it turns out I didn t need to pay). Either the TPS I bought is bad, or the pigtail to the connecter has a broken wire (?).

What s the TPS diagnostic procedure?

Would that cause the surging/missing?

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Monday, September 24th, 2012 AT 12:35 PM
Tiny
HMAC300
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Surging a lot of times is the throttleplate and iac valve are dirty. Clean the plate on both sides and clean teh iac hole with choke cleaner, that normally does the truck. It may be part of th tps problem as well as the plate may be sticky. Here is the chart for that code.

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Monday, September 24th, 2012 AT 1:52 PM
Tiny
SATURNTECH9
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A bad tps input can cause hard shifting high idle dieing when you start the car etc. Just went thru with my car I had a bad tps connector. The first thing I would do is diagnose the tps code that will more the likely fix your problem.I have never personally seen a sticky throttle body or iac cause surging while driving a steady speed down the road.

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Monday, September 24th, 2012 AT 3:15 PM
Tiny
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I finally got a chance to work on the car Sunday. Here s what I did.

I got a 3M fuel system cleaner kit, and cleaned the throttle body, it was very dirty, and ran the TPS tests that hmac300 suggested. The TPS appeared to be OK. The TPS circuit got 5v reference across the power to ground and.4v at the blue to ground. Had a friend operate the throttle, and the VOM showed a smooth voltage up to just under 5v. So because I couldn t seem to find a problem, I replaced the TPS with a new one I replaced it before when I first got the car, and the part had a lifetime warranty. I then did the tests again to make sure that everything was OK. I found a rotted vacuum line, replaced it, and checked all the other lines. There was a hole in the fresh air hose where the PCV comes in to it, and I patched it with RTV until I can find a junk yard part to replace it. I sprayed carb cleaner on the throttle body, and around the manifold, and didn t get any idle changes. Then I reset the code (22). Maybe the problem was a loose wire, and, it tightened up when I pushed the pins into the connector to test it (?). Should I replace the plug if the problem comes back?

I test drove the car and the light came back on. This time it was a 32 EGR diagnostic switch incorrect EGR valve operation. I reset the code, and didn t drive again until today. The light came back on. I ll check it tonight to see what it was. But the car seems to be running smoother and idling better.

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Tuesday, October 9th, 2012 AT 1:13 PM
Tiny
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It probbably was the hole in the duct work as the maf couldn't work right and the rotted vacuum line, your egr may be the small controller box or aplugged egr port/valve. The controller box occasionaly failed.

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Tuesday, October 9th, 2012 AT 1:39 PM

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