My '88 5.0 has been acting a little strange. I bought the truck about a year and a half ago and just had a used motor put in this past winter, so the truck is still a bit new to me.

I've been noticing for a while that when in about second and pushing it with moderate gas, it lacks power and sounds like it is missing or something. If I stomp it and the transmission downshifts, I get power back and it seems to be fine. If I'm just putzing along in first, also no problem.

Also, it's been getting noticeably harder to start. Still turns over, fine, but takes quite a few more rotations to fire up.

Where should I start? Could it be the ignition coil failing? If it were just the starting issue, I might just suspect the battery, but the alternator should be doing the heavy lifting during moderate acceleration. I haven't tried pulling a plug yet to look for fouling there.

Thanks,

-Dan

 

If the ignition coil was failing the truck wouldnt be picky about how it acts in only certain gears. To be honest it sounds more like the transmission is having several issues.

 

I can't be sure about the gear. The behavior I notice would be like if I were just cruising along at highway speed and attempted to slowly accelerate. Instead of strong acceleration, I get a very slow acceleration, if at all and I near quite sounds that I'm interpreting as missing. It this starts to happen I can either let of the gas, and things sound normal again, or I can stomp it and force it to downshift to a lower gear. I get power back and everything sounds normal.

Edit:

Ok, I'm also reluctant to consider it a transmission problem as the thought of needing tranny work $cares me. I will speak up here though and mention that something else is going on with the transmission right now. If the car hasn't warmed up, it won't engage from park/reverse to drive right away. If I come to a complete stop and don't change the selector even then sometimes it doesn't take off when I hit the gas. I haven't checked yet, but I'm wondering if the fluid is low. I'm taking the truck to a buddy's shop tonight to get tires put on. I know I need to look for leaks in the brake lines (slowly loosing brake fluid). We can look for a transmission leak at the same time and check the level. I have not heard any strange transmission sounds along with the problems. It simply acts like it is in neutral, then suddenly decides to catch.

 

The cranking likely is the heat of summer and the starter. Dunno about your power issues.

 

i would check your plugs and wires at low rpm you have less voltage going to your plugs. high resistance could make the spark jump to a bracket, manifold, or something. when you rev up it increases voltage and jumps to your plug. have you replaced the rotor, or distributor cap?

 

I thought the rotor and cap was replaced as part of the engine install, but looking at the work orders, I don't actually see a line item for replacing them. I think I have a whole distributor from the old engine in the garage. I could easily swap out the cap and rotor. I do see that the starter is brand new.

-Dan

 

Mine's new, (well, reman.) And it still takes a while to fire up. The old one worked like a charm in the winter. This one does well early morning. Probably heat.

 

Probably not your transmission.......
Spark has less voltage at lower RPM? Your ignition should have the same voltage at all times REGARDLESS of RPM.....

So why? When you downshift, your engine's RPMs raise. When the RPMs raise your engine moves into or close to it's powerband. You make more power at a given RPM then you do at an idle or lower RPM. Your 5.0 should make it's max HP around 4500 RPM and I think the torque peak comes in around 2500 RPM.

Pull and check your plugs, wires and cap. Check for codes even if you don't see a check engine light. Vacuum leak? Have you checked the Compression of your used engine? Timing could be an issue here as well. Many things can cause drive-ability issues at low RPMs.

There is an answer and it is not RPM dependent Spark Voltages.

 

The transmission was two quarts low (whoops!). There seems to be a leak at the cooling lines. It looks like maybe one line was replaced already, though it must have been years ago. Still not likely the engine problem.

I don't have a compression tester, but I guess I should test that. I would have thought they shop would check that before selling me an engine. Too bad the warranty is only 90 days. Spark seems like the easiest place to start and to replace.

FYI, got 31s put on yesterday. They rub a bit if you turn the wheel all the way. Maybe I should get spacers? Need a set of lugs though. The metal covers torn off of most of them. I think it took us four different size sockets to get all the lugs off.

-Dan