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Well, my little blue 89 Colt suffered a major failure: the driver's side door cracked at the hinge! Rather than find a new door, I sold the thing for $300. I have now found a new 91 Colt that I bought for $300! The only differences are 8V / 5-sp. in the '89; and 12V / 4 -sp. in the '91.

The 91 is running and driving, but runs very rough (both cold and hot) from idle through about 25% of the throttle opening. Then it roars to life. The CEL is on, giving code 42 (fuel pump). I changed the fuel pump and left the battery unhooked for a while, but the pesky code 42 came right back! Haven't opened up the ECU yet to check for damage.

I filled the tank after I put in the fuel pump, drove about 100 miles, and then filled again to check mileage. Got 30. My 89 5-speed consistently got 37.

Because posts with pictures are 86.5% cooler than those without, here's the old and new clunkmobiles:




Anyways, any suggestions greatly appreciated!

**UPDATE**

Finally got new cap, rotor, plugs, filters, etc in. Runs better. Swapped in an ECU from a 89 Mirage. No more CEL! STill running a little rough off-idle, but much better now when warm.

replace your fuel filter, they are only supposed to last 20,000 miles and most of us have over 100,000 miles on them. they are less than 20$ and on a 12v 4g15 they take less than a half hour to change. 2 of my 4g15 cars had the hesitation problem and both times it was the fuel filter.

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OKAY.. just to "close" this thread:

Fuel filter and regulator swapped out.

The 2 two things that made the most change are 1. Reset base timing. 2. (shockingly) ECU swap.

Car still hesitates slightly when cold but at full temp runs great. Idle swings by about 200 rpm (est.) but hey, it's a $300 car so I'll live with it.

I did a "scientific" MGP test by filling twice at the same pump until first click-off. Based on that logic, 39 mpg. I'm pretty stoked.

Thanks!!