Belt Tensioner / Faint hesitation under load - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 04-18-2005, 02:30 PM   #1
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Default Belt Tensioner / Faint hesitation under load

The belt tensioner on the back belt is jumping like crazy at idle. If I raise the idle a bit by hand, it runs smooth as a baby'* behind. The tensioner was replaced about 1 year ago. I just put the smaller SC pulley, gatorback belt, and larger idler on, but it was jumping a bit prior to this, just more agressive now. Is this normal?

I am also experiencing a very faint hesitation under heavy load. Feels like the engine is slowly building power. Can't really seem to put my finger on it (feels like it could be ignition, fuel, or even tranny, just so damn faint it'* hard to pinpoint). Under a light load, everything seems fine. New plugs, good wires, coils, etc. Just went through everything for a different issue. Read a post last night about a TSB calling for FPR replacement with a Series II n/a FPR which will take pressure to about 50 psi. Has anybody done this? It feels like it could be a lean condition, but I haven't run it with a scanner to see if the flag is being set. Any thoughts?
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Old 04-18-2005, 06:10 PM   #2
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I've tried this FPR swap. It only reduced my fuel economy, but I was suffering from an undiagnosed weak fuel pump at the time. It might be worth a shot, I don't know. I belive I sold the FPR, so I can't easily try it again.
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Old 04-18-2005, 06:16 PM   #3
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Hit me with that part #. I think I am gonna see if I can borrow a scan tool again to see if the lean flag is being thrown. I'll start there after watching the fuel pressure gauge taped to the windshield again. I have a feeling that I might be chasing a tranny problem. It'* just too damn faint to tell, but it is definately affecting performance. If pressure is good under load and the lean flag is being set, I just migiht try that other FPR. Not sure where to go with it right now.

And the tensioner is the wackiest thing. I have no clue, maybe the spring is weak?
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Old 04-18-2005, 06:21 PM   #4
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The tensioner is not normal. But I've never had the problem, so I've got no advice there.
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Old 04-18-2005, 08:37 PM   #5
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96+ L67/L36 Fuel pressure regulator

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Old 04-18-2005, 09:50 PM   #6
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OK, more on the hesitation since I just took a 200 mile cruise and checked into my hotel.

Had cruise set on "about" 80. When pulling a long grade, I noticed the tach running from 2600 to 2800 rpm (when shifting out of overdrive, if I remember correctly). Anyway, the hesitation/surge coincided with the rpm change. Is this sounding like the hesitation/surge that is all over these posts? Funny thing is, I can feel it from a hard launch starting form a standstill. When winding out first and second, I can feel the hesitation. If this is TCC surge, I thought TCC didn;t apply in the lower gears, but then, I am just a shadetree mechanic who sells office equipment and software for a living. Any thoughts would be greatly appreciated.
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Old 04-26-2005, 08:29 PM   #7
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This has been an education. Part of the problem has been solved. Pulled out the Accel injectors (they are headed back to Summit) and put the stockers back in. Performance improved dramatically. I still have a "hesitation" in the upper end of the power band felt mostly during the high end of 1st and 2nd gear. Now that I have the other issues resolved, this is very noticeable. I just replaced the bosch O2 with an AC Delco, even more improvement. The hesitation is driving me nuts. Had the tranny checked out, no slip, showing 100% duty cycle on TCC lockup in OD. I am leaning towards a lean condition under load. I haven't bought the 97 FPR and tried it, but did throw the FP gauge back on. It shows about 45psi w/ KOEO, 40-42 at idle, when driving (gauge taped to the windshield) at low speeds it will increase to almost 50 pulling a steep grade. During a hard acceleration, pressure will drop to 40-42, but when very demanding on the top end, it will drop to 36-38, which seems to coincide with the hesitation. Since I put on the 2.2 pulley, is it demanding more fuel on the top end than can be delivered? Or am I missing something else. I also just checked the MAF, shows a 2.6v output at idle and drops to 2.5 when revved. Looking for some additional thoughts before i go splurging on a 97 FPR or the adjustable unit from PFYC.

Coils have been checked, new plugs, new wires again (stock set on now). Nothing seems to be apparent at the low end.

Fuel pump and FPR have been replaced as well (pump was failing causing another type of greif). I haven't been able to borrow a scan tool to check and see if it is going lean, just working on a hunch.

Not sure what would be left unless it could be a MAF issue or maybe PCM programming?

Any thoughts would be greatly appreciated.

BTW, if I drive abnormally (just an easy acceleration and a nice cruise), no hesitation is felt until in OD and pulling a long grade, then it seems to translate to tranny "chuggle", which may be yet another issue entirely.

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Old 04-26-2005, 08:52 PM   #8
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The stock healthy fuel system is enough. Don't upgrade anything yet. Put your MAF screen back in, unhook the battery so the PCM will reset, then give it another try.
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Old 04-26-2005, 09:07 PM   #9
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Thx,

I will try it tonight and get back.

Any idea what I did with my snap ring pliers?
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Old 04-26-2005, 11:41 PM   #10
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MAF screen is back in. Definate improvement, but there is still some slight hesitation. Although, now I am starting to hear that slight wonderful pinging sound (again, full acceleration and pushing about 10 psi of boost or so - dash gauge). I am wondering if the hesitation can be attributed to KR? I have the rice pipe on, but no cold air shroud on yet. I have the stuff for it, but just haven;t built it. Should I do that next or no. I have never had to battle KR before (assuming that is what is happening). It is wet out and only about 60 65 degrees. I wouldn;t think that it would be hot enough for that to happen yet, but I have been fooled many many times before.
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