mtyson

I have been chasing this a while.

Slowly developed an intermittent hard-start issue, got to where it was like engine was going to pop out of the hood.

Finally took to Firestone, drama ensued, and discovered CPS was bad.

CPS replaced by myself, starting seemed better.

Hard-start is developing again. It doesn't seem to be fuel pump, even if I leave key on for a bit, it can occur.

Issue is like so: turn key, engine catches right away, but in the first moment, it makes a few hard-hits, like almost a hammer hitting the engine once, twice sometimes three times.

Things I've done recently:
New TPS
New CPS
New IAC
Seafoamed via gas and TB
new radiator

I noticed on the edge of the TB butterfly blade is a thin layer of black carbon... could that be sticking?

Any other ideas???

BTW: Issue seems to happen more with engine hot.

tjwalker

1. Always post year/engine in a new thread. There are significant differences through the years which will make a difference on the answers you receive.

2. Have you seen a check engine light? If so, you must pull codes for clues as to the root cause.

3. What brand spark plugs are you running and how many miles on them? How about the other tuneup hardware like plug wires, distributor cap, rotor (pre-2000 models) The importance of fresh tuneup hardware cannot be overstated for quick starts.

4. Some basic testing out of the gate would be fuel pressure. You need 49 psi to fire up the 96.5 through 2001 4.0 engines. 31 psi for earlier models. See what I mean about posting the year?

5. 00-01 models are more susceptible to "heat soak" which can be responsible for hard starting of a HOT engine. Search and you'll find lots of light reading on that subject!

mtyson

Sorry, it's a 1997 xj 4.0 6cyl awd

Spark plugs were replaced just before I bought it, about 2 years and 15k miles ago. They and the wires look fresh?

I need to test the fuel pressure.. .that'll be a new skill for me.