good MAF lb/m?

[Elcapper]

Hi, it's been a long time since my last post!

Just wondering what I should expect my MAF lb/m ratio to be? Mine read out at .75-.90 tonight at cold start about 60 degree weather. Ex didn't start earlier tonight which reverts back to an old issue I had with a no-start condition. It would turn over, sound like it was about to kick in, but nothing. Finally got it started by pumping the gas a little tonight. So that makes me think it's an airflow issue. Last time I had this issue early this year I cleaned IAC, checked relays, replaced fuel filter, cam sensor, cps - then moved it on a flatbed and it started at the end of the trip. I never touched the MAF though so just wondering if that is a decent MAF reading. Plan to clean it tomorrow and hopefully that will do the trick. I think I usually idle at about 1000 rpm's.

Sorry, I searched for the info but maybe I was searching the wrong terms or something because I couldn't find anything. Or is it just the voltage that matters?

Any help appreciated! I've read a ton of the no-start threads over the last year since I never found out why mine ended up starting eventually (wasn't after I replaced anything, just out of the blue).

Anyway, thanks!! '98 OHV

Rory

 

[Elcapper]

Okay, this morning I cleaned the MAF and disconnected the battery to reset. Then I sprayed carb cleaner all over to try and find any vacuum leaks but didn't find anything. The car started great the first time this morning. The 2nd time I had to give it gas, the third time was great.

Could my IAC just be bad? I cleaned it earlier this year (it was black).Would it be worth replacing just to see if it makes a difference?

Thanks!

 

[2000StreetRod]

IAC valve and engine start

For some time I have suspected that a functional IAC valve is not essential for engine start. Your question prompted me to perform a test. Today I disconnected the electrical connector to the IAC valve and then cranked the engine when cold. The engine started immediately and then within a few seconds ran rough and started to die because the IAC valve was not controlling the idle speed.

If your engine starts but won't idle then it could be your IAC valve. However, in your first post you stated that the engine would not cold start until you opened the throttle plate. Try to determine if the engine starts because you pump the accelerator or just because you open the throttle plate. If it starts because the throttle is open that indicates excessive richness at closed throttle. If it starts because of pumping the pedal that indicates a lean start condition.

I suggest that you check the fuel pressure. Or, cycle the ignition switch from off to Run three times before cranking the engine. If that makes a difference, then your starting problem is probably fuel pressure related.

You may also want to test the TPS which could be providing incorrect voltage readings to the PCM. See TPS Test Procedure

 

[Elcapper]

Thanks for the reply!

I haven't been able to replicate the no-start condition again yet so I haven't been able to check whether it starts if I open the throttle plate yet. I'll do that with the next no-start.

I tested the TPS and it came out good. .94 at closed, 3.74 wide open with no jumps on the way up.

I just moved and haven't been able to find my fuel test kit, and not sure it works anyway as I wasn't able to get correct readings the last time I tried it - I mean waaaay off- the kind that makes you think you're probably not doing it right. (which I probably wasn't even though it should be pretty cut and dry)

I'll give some new info as soon as I can. Rory

 

[Elcapper]

I found my fuel pressure tester and confirmed the valve that screws onto the schrader valve is busted. Ordered a new one from Amazon and will have it Wednesday and will post the results.

Thanks!

 

[2000StreetRod]

unscrew the valve

You can unscrew the valve and use a hose clamp to connect your fuel pressure gauge. Some members always do that to get an accurate reading.

 

[Elcapper]

I was able to test the pressure tonight.

36 at the On position
30 at idle
35 throttling, with no falls when pressed fast.
30 after turning off, slowly climbing up to 36 within a few minutes.

I think these are pretty normal readings for a '98 right? Does that pretty much rule out a fuel delivery issue?

It's been starting pretty good the last few days, but in the afternoons when it's hotter it's been having the most trouble. I'm not sure what to think!

Any ideas? Thanks!!

 

[2000StreetRod]

Disconnect vacuum line to FPR

For a more thorough test I suggest that you disconnect and plug the vacuum hose that connects to the fuel pressure regulator and then read the fuel pressure. The pressure should be significantly higher than at idle with the vacuum hose connected.

The fuel pressure readings that you have obtained indicate adequate pressure for the engine to start.

Since you are able to read your MAF sensor airflow I assume that you have a scanner. I suggest that you monitor your intake air temperature and your engine coolant temperature to see if the values are reasonable.

 

[Elcapper]

Thanks for the reply!

When I tested fuel pressure with the disconnected hose to the fuel pressure regulator (which I replaced last year) the pressure went up to 39. So ten over idle pretty much.

IAT started at 79 degrees and crept down to 75 over a few minutes of idling.
coolant temp started at 140 and crept up to 173 over the same time period, maybe 3 minutes.

Do those figures sound right?

 

[Elcapper]

I replaced all the plugs today (new wires arrive tomorrow). I started the car fine after 3, and then after all 6. Then I tried starting it again and it wouldn't start. So I had someone turn the key and I hit the throttle under the hood. Car started right up. Then I got in the driver's seat and turned the key and tapped the gas and it started up also, although it was a close call.

I just noticed my AC condenser is cycling on and off with a loud "chnk" sound repeatedly every few seconds. Based on searching other posts sounds like I need a recharge. Didn't notice it before so I think it might be new. Anyway, I don't think that would have any effect on my intermittent starting issue?

Any new ideas? Should I invest in a new MAF? I forgot to disconnect it and see if it starts but will try that if it fails again.

Thanks! Rory

 

[2000StreetRod]

temperatures

I thought maybe your coolant temperature sensor could be reporting the wrong value to the PCM resulting in an incorrect fuel mixture for engine start. Your temperatures seem reasonable.

Being low on refrigerant should not affect the engine starting.

I'm puzzled about tapping the throttle and the engine starting. I wonder if it was related or just a coincidence. You've already tested the TPS voltage and it is reasonable. If the connector is loose and not making connection then the PCM would determine the voltage is out of range and set a DTC. Have you monitored the TPS with your scanner at engine start?

You've replaced the camshaft and crankshaft position sensors and the spark plugs. When the engine starts does it run well under load and at high engine speeds?

 

[Elcapper]

It didn't feel like a coincidence when I hit the throttle and it started, but it could have been. I felt like I waited long enough while the engine was turning over before I hit it.

No, I haven't monitored the TPS at engine start with my scanner, but I will check it tomorrow night and see what it says.

It seems like the engine runs well under load and at high engine speeds. Nothing seems to add up - it's really frustrating!

 

[Elcapper]

I switched out the wires tonight and it started okay afterward. One thing I thought was really weird and would like to see if this is normal is the layout of the wires. Looking at the engine from the front of the car:

Left side looked good with wires 3, 2, 1 in order from back to front matching up with the plugs in the same spots. On the right side though, the middle wire went to the back plug, the back wire went to the front plug and the front wire went to the middle plug. Is that normal???? Seems wonky.

My Abslt TPS reading went from 0 in the on position to 18.4 at Idle. Under acceleration it would rise to around 34 or so and fall back to 18.4 at idle again.

Ign Advanced (deg) started about 12.5 and climbed up to 16, then fluxuated from there back down to as low as 9 at idle and then 20 max under acceleration.

Any ideas from any of that info? Thanks a lot I really appreciate all the help!!

 

[2000StreetRod]

firing order

The firing order for the V6 is 1-4-2-5-3-6. The coil pack numbers are:
rear
3 4
2 6
1 5
front

Your scanner should read and display the TPS value with the ignition On and the engine not running. A reading of 0 with the ignition On sounds abnormal. With my scanner I can slowly depress the accelerator with the engine off and the ignition on and watch the TPS Absolute increase from closed throttle to WOT. Other than the 0 value, your TPS and ignition advance numbers seem reasonable.

Intermittent problem sources are difficult to identify. You might try cleaning the contacts on the crankshaft position sensor by disconnecting and connecting the electrical connector a couple times.

 

[Elcapper]

You're right, I must have read that wrong - my TPS was 18.4 at on position and then went up to about 90 at WOT.

Yeah, I'm bummed out about the intermittent thing. I guess I'll just keep hoping it doesn't happen in the mountains!

Thanks for your help diagnosing! I'll post if anything else changes.

 

[Elcapper]

old intermittent start, new symptom

Hi, I have an intermittent start where I have replace tons of stuff. Anyway, we went through a cold spell here and then it's back up in the 70's. The car started way better during the cold weather than when it's hot. Now I'm back running into the same starting issues.

Once I get it started, I can drive somewhere and never have another problem until it sits for a few hours in the hot weather.

I tested fuel pressure and it's good. I replaced crankshaft and camshaft sensors and IAC, cleaned MAF, tested TPS, etc...

Based on searches here and google, it looks like PCM relay or fuel pump relay, both of which I have replaced.

Any other ideas? Should I replace the MAF? Check under the power dist box to test for bad connections? Can't be too many things since it's related to temp outside can it?

Thanks for any insights!