Pickup developed low power issue (won’t go over 35 unless downhill) suddenly, I’m told. Already had other issues. Replaced the engine with a used one, replaced the MAF sensor, and replace the ECM. Took care of all issues except low power. In neutral RPMs top at 3000. New fuel and air filters, distributor cap & rotor, plug wires. Runs smooth, idles fine, just no power. anyone have an idea what else could be wrong with this one?
The first things to suspect are low fuel pressure and restricted exhaust. A vacuum gauge will help determine if there is an exhaust restriction and a fuel pressure tester is needed to check the the fuel. Whoever installed the engine should have those tools.
And for gosh sakes stop throwing parts at it! I think throwing another engine in it is just about the most extreme version of parts changing I’ve ever seen. Unless this was done for some other reason?
Your subject mentions OBD1 - but the post mentions no codes. Are there any?
Engine was changed because it had over 200,000 miles, used 2 quarts of oil per tank of gas, and had very low compression on 2 non-adjacent cylinders. MAF sensor was changed because it would not run with it plugged in, $30 for a good used one. Since that didn’t change anything, and it is a direct feed to the ECM, that was the only other culprit left. No codes. when it reaches 3000 the engine really sounds like it is laboring. I suspect the exhaust as well and will have that checked. I’ve spent $1500 on this vehicle including the purchase price so I still have a little room to play with.
vacuum gages are fairly cheap - what kind of reading would you be looking for with restircted exhaust? It looks like the 3 bolts at the cat convertor will require a blue-wrench to get loose, so that’s not an option for testing at the moment.
Here’s a great guide to the vacuum gauge - scroll down to “The Readings.” “Scenario 14” gives clogged exhaust: http://www.secondchancegarage.com/public/186.cfm
Before I had a vacuum gauge I once checked for an exhaust clog by just pulling a front O2 sensor - opens the pipe without having to disconnect. A vacuum gauge is better.