Terrh

iTrader: (7)

1987 TII, stock aside from a catback and turbo timer.

Just picked it up recently and trying to sort its issues.

It has the 3800 RPM hesitation, sometimes so bad it won't rev past it even at WOT. Cold idle is non-existant (nor is hot idle after a restart) but it idles rock solid any other time at 850RPM.

Once you're past 4000, it pulls strong all the way past redline. Feels very healthy for a stock S4 TII actually.

What I've done so far to try and fix it:

Adjusted the TPS.

Checked for (and fixed) many vacuum leaks. The FPR was disconnected, and one of the vacuum solenoids was too, so I reconnected both.

I redid the battery terminals, ran a new 4AWG ground to the block and 8AWG to the body. Pulled the UIM and cleaned the ground under there and reassembled. That didn't fix it so I pulled the passenger carpet and soldered the 4 ECU ground wires and added a ground to the chassis.


Still not fixed, and the hot start issue that I previously fixed is now back.

It's not your usual hot start issue either. Basically if the car sits after running for more than 5 minutes and less than an hour it'll stall immediately after starting, especially if you give it any gas. Takes about 10 tries to get it started, and once it does start if you give it any gas it'll die until it's been running for about 20-30 seconds, then it's fine. It /never/ floods and is always easy to start aside from it stalling immediately after.


Any ideas on what I should look at next?

I'm also on the opposite side of the country from my pile of FC parts so part swapping is not really an option.

lduley

iTrader: (1)

compression test
injector service

in that order, than report back

misterstyx69

iTrader: (142)

Check both Water temp sensors Daniel.
The one at the bottom of the rad and the one at the back of the WP.

Craze8

Sounds familiar. Mines accompanied with lean running. My old ecu went up in smoke or so I thought. Thought might have been a VAF issue, seems I cant get a reman one thats worth a damn as everyone I have installed has exhibited the same no run issue. were as my original does run the car. Compression on mine checks fine. Never thought to check the lowwer coolant sensor on the radiator, the one on my water pump is less then 3 months old new OEM. I had replaced the TPS and fuel pump that was weak. Like you, I've gone through all my grounds from one end to the other.

I'll look up the test procedure for the lowwer radiator sensor thanks

Craze8

Can't really find a test procedure on the lowwer sensor in all data or looking through the FSM. On an 80* day with the engine cold it reads .4 ohms. Is this sensor a PTC ntc or just a switch?

satch

iTrader: (1)

It's a switch having only two positions.

Terrh

iTrader: (7)

Working 70+ hours a week so sundays are my only day to investigate issues.

Compression is fine, and I don't see how this could be a compression related issue, but I did check it and got 105 front and 110 rear, so that's awesome.

I did run some injector cleaner through it, but I don't think that the injectors being dirty could cause this either. I might swap the primaries and secondaries when I get my hands on a UIM gasket though.

Plugging the FPR in resulted in improving the MPG a ton, wonder why? :P I got over 450KM on my last tank of fuel, 75% highway but generally cruising at 130+km/h. Pretty happy about that.

I noticed some goofy stuff on this engine when doing the compression test today. There's a big piece of rusty iron around the trailing plug on the front rotor, doesn't appear to be attached to anything but just there. Never seen that on one of these before. My plugs look kinda worn, I'll buy some this week.

On the coolant sensor subject:

On the back of the thermostat housing, there are two sensors (in addition to the one on top).

The larger one has two wires coming off of it that aren't hooked up to anything, what does that sensor control?

I took a picture of it:


Rest of these pictures are plugs that aren't plugged in to things. I'm pretty sure these are all plugs that do nothing, but if someone could verify that I'd appreciate it.

Oh, and the one solenoid I circled was the one that was disconnected and when I reconnected it it cured the hot restart issue until I messed with the car more. I really want to de-emmissions this thing.

Rx7troubleshooting - Album on Imgur

Terrh

iTrader: (7)

I'll give this a bump!~

Terrh

iTrader: (7)

Bump it!

RotaryEvolution

iTrader: (30)

check the TID, we all know how crunchy that gets and is usually a cause of a large vacuum leak which will cause these symptoms, if that isn't it then i would try to borrow a known good AFM.

all the above failing check the voltage to the fuel pump, not uncommon to see 6v back there when the electrical gets bad enough.

in fact check everything for vacuum leaks including a simple loose intercooler.

the sensor you pictured is for the AWS, it shouldn't cause these symptoms that i have ever seen, nor have i ever seen it located in such a strange place as they put it on your canadien cars..

MidnightOwl

I had almost the same exact problems with my 87 TII swapped into a vert.


My hot start problem was solved in this thread:
https://www.rx7club.com/2nd-generati...oblems-499744/

I put a switch on the wire in the glove box and I have had zero problems starting it ever since. Just read through there to see exactly which wire it is. I did it almost a year ago, sorry!

For my hesitation, I got rid of any leak, serviced my injectors and cleaned all of my grounds. Grounding the boost sensor directly to the chassis fixed it for me, I can't recall the thread that recommended it, but it fixed that issue 100%.

welfare

what is the function of this sensor? i installed an s5 rad in my s4 and i guess the s5's are not equipped with it. at least not in the radiator

Terrh

iTrader: (7)

Thanks for the replies guys!

I got new shifter bushings in it today and can actually find gears when I drive, which is nice.

I'm going home in two weeks and when I fly back out here I plan on bringing every small sensor and an AFM with me since I have tons of them out there.

I have not re-done the boost sensor ground but I did re do all the rest. I guess it wouldn't hurt to add another ground there.

This engine has all sorts of weird stuff going on, but I attribute most of it to it being a JDM engine.

Terrh

iTrader: (7)

Bump

satch

iTrader: (1)

When the coolant temps are above a particular threshold the S4 engine will have the high rev cold start feature and the sensor used to check the coolant temp is the coolant switch in question. Thus the sensor tells the ECU when it should and should not operate the cold start high rev process.

Also, when the wire running from the sensor to the ECU is grounded when the car is idling there is a subtle change in the tone of the engine thus it affects the running of the engine to at least some degree.