99 Ram: won't start, or won't idle

[kevm14]

I have had intermittent starting issues with this for probably most of the time I've owned it. I thought it was the fuel rail prime. Maybe it still has that issue. I am not sure this is related, so with that out of the way...

What it did today was crank, fire, and die. It did that again. Then it would just crank and not fire. So I'm thinking...OK, the fuel pump finally died? But I could hear it when I cycled the key. Next I tried some throttle to see if I could get it to start or stay running. That actually worked. And it seemed to run fine but if I let off the throttle it would die.

My first thought was TPS. So I got out my OBD-II scantool and checked the data stream. KOEO, TPS was like 13% with no throttle and like 75% at WOT. I thought that was wrong because on my Caprice, it would actually read the full 0-100%. I've seen many OBD-II cars that act weird with respect to the TPS so that wasn't enough to call anything since I have no idea what is normal for this truck. I looked in the datastream for TPS voltage and....nothing. The OBD-II generic stream sucks. My Caprice had TPS voltage.

But what I could do was unplug it and see what changed. So I did that. The ECU strategy was to fix the TPS @ 100% which makes sense. Didn't run any differently though. And immediately popped a TPS code for open circuit so that all seemed as expected.

My next logical place to go was the IAC. On this truck it is at the rear of the throttle body. I defaulted to the way the IAC system works on my Caprice to troubleshoot. I turned the key on with the expectation that the IAC would try to go to the park position, then unplugged the harness, and started the truck. It started and idled at 750 rpm but obviously had no IAC control. I plugged it in while running. No change. Shut it off, restarted, and everything seemed normal. Normal idle flare, normal settling to idle, everything. Hmm. I sprayed the plug and IAC with contact cleaner and worked the plug a few times. Not sure what that was about. I should probably try to blow some carb cleaner down the IAC passage and make sure the plunger wasn't like stuck in some carbon/oil junk or something. Or maybe it just will need an IAC soon. To be continued (it is behaving at the moment)…

BTW, this is why you should not let issues build up, because it makes fixing new issues really confusing. You may wrongly assume the new issue is the old issue getting worse when it may be completely unrelated. That would send you down a completely wrong path potentially.

That said, it MAY be related as the old issue is that on some (not all) cold starts, it idles poorly and low and that may simply be because it wants a higher idle when cold, and the IAC isn't letting enough air pass to get the idle up where it needs to be on cold start.

[kevm14]

Geez. I went out to move it so I could clean out the IAC. When I turned the key to on, everything completely died. No power of any kind. No headlights. No dome light.

Wiggled one of the battery ground cables and it sparked so obviously that needs attention. I think I leaned on this area when I was originally looking at the IAC/harness so apparently the connection was getting bad. This does not seem like the OEM cable end. It's just three wires jammed and clamped.

I took it apart, rewound the wires which probably also helped scuff them up, sprayed contact cleaner on everything, wire wheeled the upper plate, and wire brushed the terminal itself. I reassembled with lots of dielectric silicone to prevent corrosion. It wasn't really that bad too be honest.

Reassembled.

Guess what - it cranks noticeably faster now. Imagine that. Glad I caught this at home. Maybe this was related to my battery issues.

Now I can move onto what I was actually working on. Love that...

[kevm14]

Here is the IAC and plug.

I gave the throttle valves a good cleaning with carb cleaner. I also sprayed a lot down the IAC ports. It stalled plenty of times of course. But yeah I think I cleaned it out pretty well. We'll see how things work. Between this and the battery ground, this may startup a whole lot better. I look forward to the next cold start.

This engine management is almost as simple as my Caprice. It has 6 more injectors and a rear O2 but otherwise seems to be the same amount of sensors. Nothing wrong with simple...

IAC ports are at the rear above the valve. I could have cleaned the TB with actual q-tips or paper towels or something. I just sprayed while trying to keep it running which did take care of a bunch of stuff at least. I admit this is a half-assed cleaning.

I am going to see if I can find a good used air box. The rear tabs are all broken so the entire rear of the airbox kind of leaks air past the filter.

[kevm14]

$61.19 for the OEM Mopar part on eBay. Used my TV parts balance again...

[kevm14]

Delivered.

[kevm14]

Installed my new airbox half. Before I did that, I cold started it to move it in front of the garage. It cranked and started pretty well. I don't think the idle flared as much as I think it should have but it did get right up to 1,000 rpm and stay running so that is obviously a huge improvement.

Check out all 4 broken tabs on the old one (on right).

I had to swap over the 3 clips as well as the lower retainer. A little tricky. Releasing the tabs took a bit of messing around with a screwdriver but I got the hang of it (was trying not to break anything). The lower retainer popped right out of the old one with a firm push, but required significant force to go into the new box, despite my use of silicone spray. Kind of annoying that the new part didn't include the clips and retainer actually but I knew that going in.

Really sprayed and cleaned the TB and blades. Also sprayed a ton into the IAC port (engine off).

Installed.

Cranked a while and then idled rough with all the carb cleaner in the intake. Eventually it smoothed out. I will say there is less intake honk with the air box sealed. I was getting extra manly sound at like 1/2 throttle before. Filtered air is good though...

Hopefully my soaking of the IAC cleaned more and it will idle flare better on the next cold start, which I will do today. If not, I may try to remove the valve to clean the pintle and seat. Not sure if I should do that without a new gasket in hand though.

[kevm14]

Cold start @ 45F. Just turned key to crank, no waiting to prime the fuel system. Idle flared to maybe 1400 and settled normally. Fixed forever?

[kevm14]

Same thing. About 46F. Turned the key right to crank, fired up, idled normally, no issues at all. Cranked well, too. Maybe it really is fixed forever.