93 Sundance poor idle, weak power

BUSHHAM

MEMBER
1993 PLYMOUTH

93 Plymouth sundance 2.2L, auto, throttle body injection, 180K. This model has no EGR, no MAF. Has weak power and hesitation, erratic idle, may stall at idle, may be hard to restart but always does. Does not matter if hot or cold. Some months ago fuel pump & filter failed and was replaced sometime before this problem started. Recently son has replaced plugs, wires, dist cap, coil, MAP, idle air control, O2 sensor. Have tested TPS, OK. Coolant sensor tests OK. NO codes and scan tool appears to indicate normal engine temp, advance, and other parameters. Can't find any connector problems or Vac leaks. I wonder if timing belt may have slipped to tooth or two on the cam? Is there an easier way to check this than cover, pulley, belt removal? Any ideas? Car is not worth cost of a dealer visit.

5 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Check the coil primary and secondary resistances see below and check for an excessive backpressure in the exhaust system to rule out a bad catalytic converter.

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Thursday, November 22nd, 2007 AT 4:36 PM

BUSHHAM

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4 POSTS

It may be a bit difficult to check back pressure with no EGR port and I would expect it to have little effect on erratic idle. The coil was just replaced, or do you mean the primary wiring resistance and the secondary plug wires which are just a few weeks old? I don't have a wiring diagram. I have gone ahead and taken the timing belt covers off and am trying to find out what the proper alignment of the timing pulleys are. The timing belt is in poor shape and it appears that the cam is off by one tooth. Is the small elongated hole (1/4") in the cam pulley suppose to be exactly at the top and aligned with the center line of the cam and the crank pulley when the crank TDC point is at zero on the flywheel mark?

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Thursday, November 22nd, 2007 AT 6:25 PM

RASMATAZ

MECHANIC
75,992 POSTS

See below

www.eautorepair.net

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Thursday, November 22nd, 2007 AT 7:48 PM

BUSHHAM

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4 POSTS

Thanks for the timing belt drawings.I found the cam timing to be correct, but the belt is a bit frayed and should be replaced if I can fix the real trouble. So back to square one on the real problem- I measured fuel injector resistance at about 1.9 ohms, normal I think, but can't prove anything as to how well it is working. Engine vacuum measures about 21in max at the MAP. Basic ignition timing is correct at 12deg BTC. It can't hurt to double check new plug wire resistance in case one or more was pulled apart. I removed and checked the two month old #1 plug, it was very clean. I can't verify fuel pressure at this time, have no line fitting adapter. I don't see a clogged filter affecting idle this way, when I can steady cruise at 40mph to 60mph. Do you know how much resistance to ground or battery I should measure if checking at the injector cable connector pins?

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Thursday, November 22nd, 2007 AT 8:55 PM

BUSHHAM

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4 POSTS

After all this trouble it was back to basic troubleshooting. The filter was perfectly clean, not stopped up at all. The fuel pump had been replaced, but had it gone bad? Found an old pressure gauge and hose and rigged up a pressure test directly to the feed line disconnected from the TBI. Had no spec for this sort of test but it had to read significantly more than 15PSI to allow the regulator to work properly. The pump was bad, only producing a weak 9-12 PSI (and it was noisy)! Directly connected, the new pump would easily produce 35PSI of unregulated pressure with just a short on cycle using a wire jumped across the pump relay socket. This replacement was still under warranty from Advance Auto Parts so we swapped it for a new one. I have heard after market pumps are typically poor quality.