hard starting

[jcwaters1]

hey, i have been having a problem with starting my 98 4.0 SOHC since it has been cold. it cranks for probably 4 seconds before it actually turns over. yesterday it was really bad, cranking for about 5 seconds, and it wasnt any colder then usual. and last week, the first crank sounded like my battery was dead, but then it cranked just fine and turned over. i have heard: IAC valve, upper intake gasket leak, fuel check valve, and various other things. any ideas or experience?

 

[2000StreetRod]

check the battery cables

If it's cranking slowly I would check the battery cables and clean the battery connections.

If it's cranking normally but not starting I would clean the IAC valve and MAF sensor. Then I would check the fuel pressure. If you happen to have Bosch platinum plugs some members have had problems with them.

How did you determine your 250 hp performance? It seems high for the mods you have performed.

 

[jcwaters1]

their autolight double platinum plugs i think. but yeah thats what i was thinking i start with the iac valve. thanks

 

[jcwaters1]

update on this problem. my check engine light has been going on and off periodically so i got a code reader and it said that one of the O2 sensors had a slow response. is this what could be causing my problem? i checked the iac valve, and its dirty, im gonna clean it up this weekend, and the 2 O rings are a little bit smashed/not completely O anymore. any thoughts?

 

[jcwaters1]

any thoughts anyone? im kinda in a hurry to figure out what the problem is, i get my paycheck tomorrow and will be able to get parts if needed.

 

[2000StreetRod]

Not the O2 sensor or 8 gasket

update on this problem. my check engine light has been going on and off periodically so i got a code reader and it said that one of the O2 sensors had a slow response. is this what could be causing my problem? i checked the iac valve, and its dirty, im gonna clean it up this weekend, and the 2 O rings are a little bit smashed/not completely O anymore. any thoughts?

When you start the engine the PCM is in open loop and not using the O2 sensors. The 8 shaped gasket gets flattened when the IAC valve is tightened down. Even if it were leaking it shouldn't cause hard starting. Don't be anxious to buy parts until you determine something is broken. Solve the hard starting problem before the sensor problem.

If your air filter is new or recently oiled it could have contaminated your MAF sensor. If you still have hard starting after cleaning the MAF sensor and the IAC valve then try performing some of the tests identified in My Helpful Threads. I suggest the TPS, MAF sensor and Fuel Pressure test procedures. If its been more than 30,000 miles since you replaced your fuel filter I suggest you replace it and then add a bottle of fuel injector cleaner. That could avoid fuel pump failure.

 

[jcwaters1]

ok...update: i cleaned the maf and iac, no change. got a fuel pressure gauge today, havent tried it yet. not sure when the last time the fuel filter was changed..i bought the rig used. tps reading .89 volts-4.59 volts closed to wide open. i run fuel injector cleaner through once a month...roughly..usually likt every 2 months. whats next?

 

[2000StreetRod]

MAF test & fuel filter

. . . whats next?

MAF Sensor Test Procedure
Replace fuel filter

 

[jcwaters1]

aright, ill do that tomorrow probably. im starting to lean towards a going IAC. could be a combination of fuel filter and IAC, im going to run some tests tomorrow.

thanks

 

[jcwaters1]

i have been monitoring what works and doesnt, and when i turn the key on, and let the pump run briefly, turn the key off, then start it, it starts right off. what would this indicate?

 

[2000StreetRod]

Slow pressure increase

I suspect that it takes a little while for your fuel pressure to reach the normal value. The 98 model has a return fuel system with a fuel pressure regulator on the fuel rail. You could have a clogged fuel filter slowing fuel flow, a weak fuel pump or a faulty fuel pressure regulator. I suggest that you monitor your fuel pressure at ignition turn on before and after you replace your fuel filter.

I'd still like to know how you determined that your engine is producing 250 hp.

 

[jcwaters1]

now that the weather has been getting warm, it hasnt done it. it was only when it was cold that it got relly bad. i'm gonna get around to the fuel filter eventually. hvent had time to change it yet. would the temperature thing be a sign of a vacuum leak that got worse as it got colder?